Some people have a hard time saying even in text that they suffer from an affliction or have problems. Its safer to say its a friend because they never have to admit to themselves that its their problem
I think they do it so people will be brutally honest. Like usually when you ask a question about yourself, I guess people don't want to hurt your feelings so they are extra nice about what they are saying or they give you a higher rating (if it's a question about looks.
I think because some people feels embarrassed about asking questions. This is supposed to a a safe online community but I'm guessing some people don't want the embarrassment and some responses can come of a bit judgmental at times. We are all here to help each other.