Ever look at the TikTok channels for prominent celebrities? The content is horrible. It's embarrassing to look at their channels. It's inherent to the format. The sole thing propping up TikTok in the US - which is already beginning to fade - is the popularity of young people cloning mediocre dance routines. There is only so far for that one trick pony to go, it becomes increasingly boring with time.
Facebook persists as the telephone that every house has, along with its protective moat in Instagram. TikTok has no persistence reason to exist long-term. It's far easier to build the next fad social network than it is to replace something perma entrenched like Facebook. The over 30 crowd is the majority of social media users in the US, they aren't going to abandon Facebook, it's set (exactly the same way Google is in search); young people however will abandon TikTok for the next cool trinket social media app as they get increasingly bored with TikTok and desperate for something new and cool to play with.