For a lot of people, facebook basically is the internet. The same way AOL was a long time ago. Everyone they want to talk to as they go about their day is there. Basically every business in the US that bothers with an online presence at all either has a facebook page or exclusively has a facebook page. Craigslist is being eaten by facebook marketplace. Even Facebook messenger is still a wildly successful chat app and it's like... their 3rd or 4th-place messaging platform.
Facebook has become a sort of digital town square that is a pretty significant part of the economy; the real-world brick-and-mortar economy. Tiktok and instagram are much more recreational.