Two reasons. One- my brother is on the ASD spectrum and that is how he wishes to maintain a relationship with me. I would not have one with him otherwise.

Two- I live in a town that I hate and where I have no friends, but old friends of mine use Facebook, so it's a way I can keep in touch with people I know and maybe go and visit them one day.

I don't like Facebook, but it's a necessity for me at the moment.