I read this to mean that everyone uses it because it's rude to be the first to leave a party. I always kind of felt that way on social networks, in the same way as even if you don't want to talk to someone, they're a friend-of-a-friend and you're going to have to explain it to them at some point if you block them.
There's like this whole category of people -- I'd say about 95% of the people I've ever met -- who I don't want to talk to, and will avoid hanging out with if possible, but who I don't totally loathe or anything, and I don't want to intentionally hurt their feelings. There's about 2.5% I really hate and want to confront, and 2.5% who I want to hang out with.
The reason I don't have a FB account is not because of what they do in terms of selling data, as gross as that is; it's actually because of what FB and all other social networking is. It's the 95% of people I don't have time for, the 2.5% I loathe, and the 2.5% I can always talk to in some other way. I mean, I also don't have a cell phone, and I also don't come to my door when people knock on it, even if I know they can hear my music playing. My friends have my private phone number and my skype account, and they can call me anytime. Everyone else can kindly or not-so-kindly f* off, and Facebook is nothing if not the ultimate, total collection of "everone else".