Why would they?
For a government to publish statements that might be interpreted as "here's how to use the things we are always telling you not to use", is a bad look for authoritative leadership who supposedly know what's best for everyone. They'd be tying their own noose with that paradox.
Plus, what do they know anyway? That's not just me having a cocky attitude - I mean it literally. Are "they" actually knowledgeable about the recreational use of these substances? The lawmakers generally seem pretty ignorant when it comes to both personal experience and doing their own research. That is why (to give an example) psilocybin mushrooms which grow naturally on the earth, and are not poisonous to humans, get classified as "schedule 1 drugs" - meanwhile the tobacco industry (an example on the opposite extreme) lobbies and makes deals with influential people in government so it can be allowed to carry on doing business as usual, even though it's common knowledge that smoking is addictive and harmful to health.
You can think of it this way: It's okay for some substances to kill you, but not okay for other substances to kill you. It's also not okay for some substances to not kill you (psilocybin, LSD, etc won't). Which substances get placed in which category is a matter that will be determined by people who have likely never ingested them and are only vaguely or anecdotally familiar with their physiological or psychological effects.
On the flip side, there are also plenty of very harmful and addictive illicit drugs in existence. So there are often legitimate reasons to regulate and take precautions. Unfortunately, once policy is written into law, it becomes difficult to change, even decades later when the public's awareness has increased, scientific knowledge has improved, and there is a better understanding of what is and isn't dangerous - and how much risk a given substance actually poses to the public.
Decisions by governments about "drugs" is anything but nuanced. And they are risk-averse.
I get what you mean though. Having a resource people can look to in order to try to stay safe seems like a great idea. But governments are unwilling or unqualified to navigate that space and all its complexities. The populous at large are also guilty of lazily looking to their governments to have all the answers instead of studying up on matters from their own initiative.
In summary, governments are not going to provide guidance on recreational substance use. However, there are educational resources such as Erowid that document the experiences others have had. In their own words, they are "Documenting the complex relationship between humans and psychoactives". And it is a complex relationship, varying greatly depending on the substance, the dosage, the individual, and even when/where/how often/with whom else - numerous circumstantial variables.