Does HE want to know? Or are you one of his former girlfriends (or a future hopeful) and YOU want to know?
There could be any number of reasons, ranging from he's a closet homosexual to perhaps he doesn't believe in having sex just for the sake of having it.
Basically, what it boils down to is that it's his business. If and when it becomes a problem for him, he'll take steps to handle it. Until then, the girls are just going to have to learn to deal with it.
