Earlier quoted context omitted.
I left Facebook. But mainly because I realised that it's a real poor way to keep in touch with anyone. Gives you the feeling that you are keeping in touch when in reality you are just sharing photos and quotes in a medium that's very noisy with adverts.
Unfortunately, there are a lot of events/organizations that organize almost exclusively through Facebook. Unfortunately, there effectively no other free platforms with a critical mass of sign ups big enough to be used in that way.
Everyone has the gmail they probably created just to sign up for Facebook, since it seems this younger generation doesn't believe in email.