I dont expect them to just choose to do the right thing for no reason, like you say, if they were going to do that then they would have already. But put them in a situation where doing the right thing aligns with them not losing power (and for individual MPs not losing their seat) and I think they would. Mostly for selfish reasons but it also helps that a lot of them are in favour of it and most of them know its the “right” thing to do.