Because some of us predicted that Western ones are going to be a pain back in the July because we knew we wouldn't gather our wits to influence them until it is too late. And here we fucking are, because long-term consequences and "no, we won't have actions for Influence" are totally not a thing until they suddenly are and everything is on fire.
It's basically sunk costs at this point: it would be nice to have them if we influenced them ~10 turns ago to prevent drift. Now it's way too costly to be viable, considering first influence is likely to not be enough, what with centuries of not doing a thing.
People were saying precisely the same thing about the eastern colonies. That didn't stop people betting everything on keeping them.
This looks a lot more like trying to lose the colonies so you can claim vindication about a previous argument, to be honest.
I also don't believe that the first influence action will do noting given the context of us helping them deal with an appalling plague. Particularly if we get the non-linear benefits of taking multiple mains of the same thing at once.