Unfortunately for a lot of people it's still necessary. I've never used Twitter myself, but for anyone whose job might make them even the slightest bit famous, whether it's an author, an actor, a musician, a professional athlete etc, their agents, managers, sponsors or publishers will always expect them to have a Twitter profile and to participate in their own self-promotion. And even for freelancers, if they don't make their own Twitter account after they get noticed even a little, there will be a dozen fakes out there pretending to be them, each with a few thousand followers too stupid to realize it isn't the real person, who will amplify any quotes from the impersonators that could harm the real individual's professional reputation. Twitter's verification system was originally supposed to help with that, but as we all know, it's politicized to the point of uselessness.

As long as literally everyone in a position of power or influence believes that Twitter is the primary forum for online discourse, then anyone who ever wants to make any real money will be expected to be on it, and will jeopardize their career if they aren't.

And if you believe that, then they'll tell you that banning people is the free market in action.