People pay for rent and various bills, you can call their version of Uber, order food etc.
If Twitter is going to pull this off they should invest heavily in the DMing UX as messaging is the real interface for this stuff. Almost like a terminal with some extra UIs layered on top.
Reference: https://en.wikipedia.org/wiki/Super-app
Remember when everyone got pissed off because they doubled the characters? How many is on Twitter now, 5000? Markdown support too. And now they are planning banking, latex, some linkedin copy cat stuff...
In reality twitter is trying to become Facebook. Facebook only didn't had banking because FED/EU didn't liked the Libra idea.
This is just basic old man 101: trying to regain the glory days of your youth.