A lot of people where I live still use Facebook. Excessively.

I'm literally the only parent from my oldest child's class who doesn't have an account. They use it for pretty much all communication related to school and after school activities. I would miss out on everything, except one of my friends is nice enough to contact me about anything important.

My partner's university uses it to communicate for all group work (and there's a ton). I managed to get my groups to use discord instead when I was at (a different) university, but his entire program seems really reluctant to change. My coworkers all communicate through Facebook groups. As does the local community association, most of my kids' extracurriculars, etc. Some restaurants and small businesses only have a Facebook page, no real web site.

In other words, it would actually be a major disruption for a lot of people.