What's the alternative? There's no realistic way to globally coordinate and enforce a ban. A direct action campaign against AI labs would only motivate increased security until sabotage becomes impossible. Starting a nuclear war would probably be enough to stop dangerous AI research, and that's only likely to kill about 50% of humans instead 100%, so it's a great improvement, but how is an individual supposed to start a nuclear war? Of course it would be better if everybody stopped, but it's a prisoner's dilemma scenario with no possibility of future rounds, so the rational play is to defect.