There’s a whole bunch of people who wanted them, and still do:
I’m still hopeful that the next expansion takes us back to Azeroth and just makes a whole mess o’ races playable, because why not? More options is always good.
Also technically Sethrak already have a female model with Sethraliss. The differences are extremely slight, body wise, but they could always do different hood adornments or eye shapes to add more dimorphism if they really want to.