Also, yeah, how sad. God forbid you play as something other then a straight male.
I can't speak for everyone else, but the reason I don't really play something other than a straight male is because... well... that's what I am. That's what I identify with, and I have a hard time getting into any other mindset.
Deviating from Dragon Age for a second, let's talk Mass Effect. As a guy in real life, watching a random Let's Play, Kaiden strikes me as pretty dang dull. Playing the game as a male character, more or less same reaction. Playing as a female character, however... there was a little something about the chemistry between him and FemShep that made me go "doki doki doki" / gave me the feels, and I really started to regret my initial belief that "Yep, this'll be my Liara run - Kaiden sacrifice, standard procedure" (not helped by how I was playing a Sentinel, which made him feel redundant as far as combat went). Seriously, I've done whole evil playthroughs where I haven't felt so heartless.
Speaking of which, female-female romance. "HURR HURR HURR GURL ON GURL IS HAUWT!!!" That's the only way I've processed a lesbian romance in the past, and I've gotten to the point where I feel really icky about even considering the option, both from a personal standpoint and from social stigma. 
As for male-male... I don't feel comfortable with that and that's all I'm going to say on the matter.
To recap:
- Straight as male feels most natural.
- Straight as female has potential.
- Lesbian makes be feel kinda bad.
- Homosexual male isn't happening.