Why do people care so much about the private lives of celebrities? Because (I assume) we're optimised to socialise in small groups, and knowing what our sibling's friend is getting up to would help bind a group together, except that now we live less in a small society, so we may not know anything about people other than close friends and colleagues, so who fulfils our need to gossip? The doings of friends-of-friends, of celebrities, and of soap-operas. I can't prove that's true, but I think it's the same need in all cases.