I think Jorick hit the nail on the head. A lot of 1x1 involves romance and for a lot of people it becomes a sort of way to project their own fantasies into reality. I'm not saying that's necessarily a bad thing, but it can seem odd to a person who uses RP for stuff besides that. With that said, I play characters of both genders and frankly don't give a damn what my partner behind the computer screen's gender is; if they can RP well then I'll take them up as a partner.