That's because you meant nothing in the game.
KOTORII revolves around you alone, which means there will be restriction on what type of choises you can make in character creation and during the game.
Still, certain alien races wouldn't be too hard to implement, and they could still invent a few if they had to, so who knows.
Supposendly, KOTOR forced you to be a human for story purposes, but the more i think about it i'm not sure what difference would have made if Revan was to be an alien...