Why does everybody say..?

Why does everybody - when asking a question about someone they know on here - always say "My friend, lets just call him H" or "lets call him bob"?? What's the point? As long as you don't say any last names then who is going to care? It's not like they will stalk you and find the boy you like. Seriously!? Why can't people just say "My friend, Timmy, went to...?" Could somebody answer this?