And countries still violate these treaties. See Iran and NK.

Also the bio/DNA ones are quickly falling apart as the technology to do these kinds of things on a small scale are readily available. To the point where we're finding illegal wet labs in the US.

Nuclear was more of an exception because of many of difficulties in purifying stuff for weapons and its detectability.

AI is a much, much, much harder problem is it uses the already existing infrastructure as a base. Unless we regulate, monitor, and ban all private usage of technology AI can be developed at a small scale.