A chat app aimed mainly at 1-1 or small group communications has a clear path to being a super app. (WhatsApp... Also Facebook has a history of having an API for 3rd party apps that integrate with Facebook, one is left with the feeling that it is serious misconduct on Facebook's part that they screwed around with Libra but never took a serious stab at peer-to-peer payments.)
As Twitter is mainly about large scale group communications it seems adding payments to Twitter might get you something more like Patreon, Substack or OnlyFans.
Another trouble I see with Twitter is that a payment app has to be trustworthy... We're used to seeing warnings on Tweets that they might be "fake news" and Elon Musk seems to have a roughly 40% unfavorable rating these days . The left-leaning half of the population is unlikely to want to send or receive payments w/ Twitter; many people on the right seem to squee as soon as they hear "TWITTER FILES" but feelings work like a ratchet and if his erratic behavior pisses off people on the right his favorables won't get any better.
The problem is once everyone is there, it becomes uncool and people start to look elsewhere.
(but maybe that's just me)