Why do people go so far to get attention?

I know a lot of people that just go so far out of the way to get attention, it makes me sick. I have…well had this one friend who was crazy in love with this guy that was the total opposite of her. she changed her whole everything and her attitude totally sucked. she was super happy when he noticed her and she stopped talking to everyone else she was friends with, but then she found out he had a girlfriend and now she doesn’t know what to do…it was a total waste of time.