Apparently it is because "They like it that way". Pretty wild if you ask me.

What's more interesting than the answer to that question is the question itself. People live that way, taking it as granted, without ever asking. Merely putting the question before them is illuminating for them. In terms of actually asnwering, I do not have to go beyond what you have said, "it's taken on a life of its own ... part of it now", though I am prepared to dwell more into the history.

Btw, the students find that question a lot more exciting than the others. Perhaps talking about the opposite sex is subconsciously more appealing to them, especially at that age.