2 reasons:
1. #Meta has to make more money. Forever. So they will embrace extend extinguish in the relentless pursuit of more and more, regardless of everything you say
2. The nagging notion to them that #Mastodon and the #Fediverse is a threat. So at least they can keep tabs on us, and, with their thumb in the pie, warp kill or coopt whatever it is *they* think we have that might be attractive
But of course what we have is we're not them: #centralized #plutocrat crap