Ya your right. It is just a safe way to know the other persons age when you get into PM's. Because, if I am talking to someone in PM's and then find out they are under 18 -- it would make me feel unwell. I would have to disengage talking with that person, and question was my statements was to adult for a minor. That is the reason I ask for age first. Sure, it could be a minor on the other side, but the risk is low, and I am sure the minor is not going to be lying of their age being as a adult.