Yeah, but even for people who don't know an "other" option is nice to have. We know that there's more than just male and female these days. ^^ And to be honest there are too many options to try and get them all anyway. XP
Trust me, I didn't do it to be rude. I just honestly had thought of it at the time. and by the time I was told, it was a little late to add it since so many had voted. That's the only reason ti doesn't have it now.
(It's awesome that you're thinking about trans people, and as long as you are, it'd be nice to get an "other" option. (And ah well I'm at it; gender usually implies preference/identification already.))