A huge reason why there aren't as many "girl" characters is because most games are made by men. Thus the games naturally caters to themselves.

I'm male. Back when I experimented with game development, all the games I wanted to make involved the main character being male. It's not something I ever consciously thought about, it's just how it happened to be. Does that make me sexist? Of course not. I can make whatever the hell game I want. You can't tell an artist how his art has to look.