Who uses their real pic for their profile??

So I was just looking at a few profiles (in a non-stalker way I swear) and can't help but wonder why so many people don't have a picture of themselves as their profile pic. And before anyone points it out, I know I haven't got one on mine but that's because i'm not out and proud at the moment but i'm working on it. So maybe one day soon I'll add one for your viewing pleasure ;) I'm just curious as to what certain people look like that's all :) Plus on some of them I can't figure out if it really is the real pic or not so if people could enlighten me as to whether their pic is really them or not. I'm not really sure why I want to know but just thought i'd mention it :)