I play WoW. And to me, it's not about sexuality either. It's more about aesthetics. In WoW, especially on the Alliance side, where me and my friends play, the male characters are really really ugly and just annoying to look at. WoW is a really cool game, but you don't really get much customization in there. I did start out playing a Human male (he ended up looking like Arnold Swarchenegger with a Michael Jackson nose) but once my friend played a trick and changed my character to female, made it look exactly like his to make us "Twins" when the character gender change feature was implemented. Ever since then I've pretty much always played female character unless I'm playing a dwarf (female dwarves are the ugliest) or a blood elf. Male blood elves are not bad at all.
Bottom line is, it's simply for looks.
Wow... I'm a freakin' nerd. Hope it helped.