I would still expect that most people on FB have a higher number of ‘authentic’ relations there on average than someone who plays Fortnite has in-game. Unless all of your friends/family play it all the time as well.

I guess it depends where do you live, though. Where I’m from Messenger is still the most popular messaging platform so most people (unless they have very strong feelings about FB) have an account.

Location/demographic probably does have a rather large impact.

There are very few close relationships that I have on Facebook. I have it because I needed an account for a while, and haven't deleted it so that it can function as a placeholder should anyone try to impersonate me.

Meanwhile, almost all of my friends have a presence on Steam - including some who I rarely if ever do or have seen in person.