Cause no one takes them seriously and it's understandable as far as I'm concerned, they are really annoying.
Still I'm not saying they shouldn't get lore but if they do, they should be the last. Draenei deserve the lore cause as far as anyone new is concerned they are just blue-ish goat people and their racial leader is one of the more important characters in the developing WoW story as opposed to the gnome leader whose only real achievement was to take up space.