Brand reputation. Every brand that chooses to use X implicitly supports X, even if they're not verified & paying X money.

I've coded a 3rd party tool that could post to mastodon/twitter at the same time around 2020 (plenty of idle time during covid). I lost twitter API access, never bothered to try to make it work again (i hate working with interface clickers). to be clear, i don't really post on social media, it was just an experiment because i had faaar too much time and thought at the time that this kind of product could be interesting.

But i would bet social media managers use similar tools, and the fact that no one can access twitter API might add just the little bit of friction you want to avoid.

No, they even would get money for the engagement they get. This is purely moral grandstanding disguised as something else.