The people who unfortunately have to get government updates from the place. After Facebook became a pain, Twitter became (for a while, when you didn't have to log in) a pretty decent way to update people on things like roadworks or weather warnings.
Joking for real, or seriously for real? The vast majority of people that used twitter are still using twitter. This applies to users in the united states, of course, but it especially applies to those in the entire rest of the world, where elon's shit largely hasn't crossed the culture/language barrier, or doesn't matter to people.