Only about 1/10 of my characters are Ace, the rest split about equally between straight, gay, bisexual. Whether or not it ever comes up, my characters are fully fleshed out characters with needs and desires beyond loot and XP. I've played recovering alcoholics who've never mentioned why they stick to cranberry juice when everyone goes to the tavern, but the reason is they don't trust themselves with a beer. Whether or not they're Ace, their sexuality is never de facto.