In Israel, every house must by law have a shelter, to protect its residents from bombs. In Gaza, apparently there are no shelters in usual houses; this is one reason why there are so many casualties from Israel's bombing.
This lack of shelters is particularly striking given the vast system of tunnels that Hamas built, which is estimated at 60 meters deep and 500 km long. Definitely, they have all the expertise and resources needed to build a shelter under every house. Why didn't they do this?
It would also be interesting to know where that GDP comes from and I doubt the aid agencies fund bomb shelters. Israel limits lots of imports and concrete/rebar in sufficient volumes may be problematic.
UN 2022 Fact Sheet on Food and Nutrition in Palestine
The number of Palestinians suffering from food insecurity is divided between the refugee (70%) and non-refugee (30%) communities. The situation is of particular concern in the Gaza Strip, with 64.3% of the population classified as moderately or severely food insecure.
It might also be counterproductive, if Israel assumes a bomb shelter under house means Hamas operatives are living there.
(something the Q doesn't really differentiate much about)
Bomb shelters
Bomb shelters, such as this one in Holon, are a common sight in Israel According to the 1951 civil defense law, all homes, residential buildings and industrial buildings in Israel are required to have bomb shelters
and in fact...
Christian embassy provides bomb shelters for towns in Israel’s north
Funds are also going to refurbish 53 existing underground shelters.
Not to imply that Israelis aren't doing most of the funding themselves. But certainly that the Israeli government merely passed a law and do not fund them for everyone. See my above points about Gazan economic circumstances... This has a bit of let them eat cake vibes to it.
Finally, there are plenty of bomb shelters in Gaza, for Hamas. Many KMs of tunnels, apparently, though their exact length is uncertain.
Did you see the images from Gaza? Apartment buildings lying on the side or ripped apart?
Israel-style "dark room with reinforced walls" bomb shelter will not be adequate against Israeli air strikes. It would fare OK against Hamas DIY rockets made of water pipe, though.
Having bomb shelters in every building is not a normal thing that countries generally require. You might equally well ask why Paraguay or Denmark do not have a law to build bomb shelters in every building, despite having the resources to do so. Not having bomb shelters in every single building is not some strange phenomenon that calls for an explanation. Rather, it is the normal state affairs.
Israeli buildings are required to have bomb shelters because Israel has a general policy of being ready for an attack against it by its neighbors. The law has been in force since 1970.
In contrast, Gaza (like the vast majority of countries other than Israel) did not have an extensive history of being afraid that its neighbors will start launching missiles at it prior to the 2014 conflict, so presumably it felt no pressing need for such law, until perhaps quite recently (again, like the vast majority of countries other than Israel).
Even if, hypothetically speaking, they did institute an obligation to build bomb shelters in new buildings in the aftermath of the 2014 conflict, in the expectation that Israel might bomb them again in the future, it would only apply to buildings built in the last less than 10 years, and therefore one would expect that most buildings would not be equipped with bomb shelters anyway.
The only way the premise of your question (that the normal, expected state of affairs would be for Gaza to have bomb shelters in every building) makes sense is if we assume that, like Israel was in the 1970's, Gaza is under constant existential threat from Israel. If you are, in effect, saying that Israel is for Gaza what Egypt and Syria were for Israel in the 1970's and what Russia is for Ukraine these days (Ukraine is another country which recently instituted an obligation to build bomb shelters in every new building), then sure, the premise of your question makes sense. But somehow, I sense that this is not a claim that you wish to make.
Edit: The intention behind the question seems to be to show that Hamas does not care about civilian lives. The argument seems to be:
"If Hamas cared about civilian lives, they would build bomb shelters in every building like we have in Israel. Because they did not do so, they do not care about civilian lives."
This is a spurious argument, not because the conclusion is false (it isn't: Hamas very obviously does not care about civilian lives), but because what is false (as illustrated by most states around the world, with a few exceptions) is the idea that if a government cares about civilian lives, they will build bomb shelters in every residential building.
Overall, using this as some kind of "gotcha" against Hamas is a bit like trying to demonstrate that the Islamic State does not care about human lives by arguing that if they did care about human lives, they would have invested more energy into enforcing mandatory seat belt laws. In other words, you are arguing for a well-established conclusion using a strange and somewhat dubious argument.
They may have the expertise but not the means to build any additional bomb shelter.
Due to Israel's occupation and blockades, unemployment is 26% in Occupied Palestinian Territory and more than 50% in Gaza, while 36% of the Palestinian population lives below the poverty line.
When you can barely find work and feed your family, a roof over your head is a rare blessing while a bomb shelter would be a luxury few can afford.
Israel also exercises control on what Palestinians can build on their land.
Gaza has been under the direct control of Israel from 1967 when it first occupied it, and indirect control (through blockades) since only 2005.
Here, construction activities are indirectly controlled by Israel with a blockade that controls the import of construction materials to the private sector in Gaza. (Israel claims this is necessary to ensure Hamas can't build bunkers and tunnels). For instance, France24 reported in 2010:
Israel on Monday listed construction materials that it will now allow into the Hamas-run Gaza Strip for projects approved by the Palestinian Authority and supervised by international observers, prompting cautious praise from foreign officials. ... The government published a list of construction materials to be allowed entry into Gaza but only for projects approved by the Palestinian Authority and implemented and supervised by the international community.
(This approach seems to be a tweak of the policy that Israel follows in Area C too, an area in West Bank that Israel directly controls by occupation, where no legal construction is permitted without Israeli permission.)
One can imagine how tough it would be for even rich Palestinians in Gaza to build a reinforced bomb shelter when Israel won't allow you to import the necessary materials, suspecting it will be diverted / pilfered by Hamas for military fortifications in Gaza (i.e. bunkers and tunnels).
I speculate that a Palestinian building plan with a bomb shelter would likely invite more scrutiny from Israeli authorities, given their suspicious inclination on terrorist activities in Palestine. As pointed out by @Fizz, Israelis were even suspicious that the opening of an underground water reservoir in a hospital was the entrance to a tunnel.
As far as the tunnels are concerned, even if civilians are using those tunnels to protect themselves, neither they nor Hamas would advertise this fact - Israel would still bomb the tunnels, with civilians, and then claim Hamas was deliberately using them as human shields.
That there is a vast tunnel network, spanning 500 kms is a claim by Hamas, that has not been verified by anyone (note that I am not disputing the existence of these tunnels, just the claims of it being "extensive" and "500 kms" - most of the photos of the tunnels shown in the media are often of tunnels on the border, used for smuggling). Israel occupied the Gaza strip for 38 years (1967 - 2005) - I personally find it hard to believe that either Israel did not know that "100's of kms" of tunnels were being built under its watchful occupation or that Hamas built "a vast network of 500 kms" of tunnels in the last 18 years despite an Israeli blockade and a war (in 2014).
The fact that Israel (or its allies) accept Hamas' claim, without question, and even repeat it as a fact in their media, is telling - exaggerating the prowess of the enemy gives them an excuse to use disproportionate weapons and force, and protects them from criticism (in the short-term) against any excess during the war.
References:
Copied from a deleted answer of Fizz by his permission. I think it is the best answer because it is an explanation given by a Hamas official, rather than a speculation.
Hamas claims it's the UN's job to build those shelters because "75% of Gaza are refugees", and so most of the Gaza population's needs should be accommodated by the UN (or the "occupation"), according to Hamas. (Translation from Arabic is from a pro-Israeli source, but I see no reason to think it's incorrect--it's a segment extracted from an interview on RT [Arabic].) A bit more searching found a transcript too.
A lot of [pro-]Israeli voices (and possibly others) interpret that [as] "Hamas doesn't care about their own people". (Yes, the search link is intentional.)
The obvious answer, that everyone in this thread ducks for, is that Hamas don't care about the civilian population/consider civilian deaths a propaganda tool.
Besides, there seems to be a culture of celebrating martyrdom among both Hamas and the general population on Gaza. Dead civilians are, therefore, not victims but martyrs, and their death is an honour, not a "problem".
Hamas does not care about the death of civilians. Besides the fact that they are not acting to protect the residents of Gaza, they are also using civilians including children as human shields.
