Because people can lie from their age to their names and look. In real life they are a pathetic loser who has never been with someone in real life and can only pick up people off the internet(Even if it won't work). This works well when they see someone's picture and they are sexy(So all you have to do is be nice and have a great personality to make thm like you.)So they hook up but it never works out cause you get tired of them sooner or later and move on to a next person.
Or...they're beverheads.