Companies and public figures keep using it, because for most of them it's just some intern or bot that was posting.
It takes a while for social media to finally die because of that. They'll just stumble on like a zombie for like a decade.
The only way it'll happen faster, is if people loudly boycott anyone that's still using it. But with 99% of social media sucking ass, there's not really a place to do it from where companies and public figures will hear it.
I'm still there because I like to know what the crazies think about stuff. It's still entertaining in its own way. For example, did you know there are business experts on Twitter even smarter than Tim Cook? It's true...
I've learned about Apple pausing their ads and about Sam Altman being fired on Mastodon. it's been becoming much better replacement for Twitter in that regard, and is only going to continue to improve.
For the same reason I started using it in the first place. Elon taking over haven't changed my user experience in any way. It's the same it has always been. Ironically enough it's also the only social media platform where my feed is 99.5% free of politics or talk about Elon.