Comment by bluGill

SMS and (to a lesser extend) email are not ways to communicate with distance friends. Someone I went to school with 30 years ago and haven't seen since isn't going to call me about their new grandkid, Facebook works well to share these types of pictures. SMS and email take too much effort, Facebook is much lower friction to share that and thus I find out, while if they uses SMS or email I wouldn't be on the list as they would give up before they got to my name in their contacts.