Okay whats the point of fb?

I created a profile to promote my book on there a month ago and joined groups to promote it. All that I’ve gotten is scammers who don’t speak much english and are too stupid to even make fun of and groups filled with spam. So whats the point of the website? I haven’t talked to a single person about my book or managed to promote it at all. Who actually uses this website? I mean seriously whats the point of it?