According to many sources, including Reuters, Israel is not a member of the Non-Proliferation Treaty (NPT), why does no one make Israel join, while they have nukes; but all of the pressure is on Iran that according to IAEA and other sources doesn't have any nukes
In theory, membership of the NPT is voluntary. Members gain the benefit of civilian nuclear technology exchanges up to a point just short of nuclear weapons capability in exchange for openness and the pledge not to cross that point. (People who pressure Iran want more than just ordinary NPT membership from them ...)
In practice, failing to do what other countries want leads to consequences. The severity of those consequences depends on the strength of the involved countries.
- There are countries putting pressure on Israel. They are not strong enough to make Israel give in.
- There are countries putting pressure on Iran. They are not strong enough to make Iran give in.
There is a tendency in Washington and in parts of the US press to equate "America," "the West," and "the international community." They're not the same. The US and their allies are just one very powerful block -- countries put to the question of either not trading with Iran or not trading with the US tend to value trade with the US more, and stop trading with Iran.
That's not primarily based on the NPT and similar principles. It is based on the fact that the US can decide not to trade with countries it dislikes, and decide whom it dislikes. No different, really, than the two blocks during the Cold War, except that the relative strengths are less balanced.