Which is odd, when you consider most forum posters in the MMO community assume every poster is a guy.
I think it's because you associate the character with the person. You see an attractive character, you think they're donning a relative likeness of themselves (especially if the character isn't an alien). Over the years (and MMOs) I've had people hit on my female characters. I was surprised to see someone call my SI attractive only because of the cookie-cutter templates this game gives you (if we had detailed sliders it would have been a different story).