Goblin shaman were clearly female? What makes you say that? I certainly never noticed it.
The assumption that the only reason gamers want females in a game is for six appeal is appalling. There are so many sixist assumptions about that that I don't know where to start. So I won't, since you're almost certainly trolling.
I'll shelve it at that-- after all, that guy is probably a troll. Let me just say that while it's fine to have supernatural daedra appear masculine or feminine, having the enemies all be male is unbalanced. I think bethesda is smart enough to make different models, one male, one female, whatever.
Also, Giants actually grow on trees, they're a kind of fruit.
Appaling? It's the truth for many people, not all of them no but it's still valid to a large portion of people. I'm not saying I disagree with you, like most assumptions it's pretty stupid, but it's not appalling.
The fact of the matter is, doing a female model for every monster is twice the work. If you consider how much time making only one quality model takes, then multiply that by the amount of models required only for monsters, you end up with an unreasonably high number in terms of development time. I'm not saying it can't be done, but there are more important things to focus on than female giants, wolves etc. If a bear is trying to rip your face off, you don't stop to check if it's a mama bear or a papa bear, you either kill it or get your face torn off. Almost nobody is going to notice it, even less are going to care if it's not a part of the game.
So doing that for common animals is almost entirely pointless. You can argue that giants are more unique and distinctive, but they're still just another enemy for you to kill or run away from. Besides, who's to say female giants aren't kept from the outside world, who's to say they exist at all? I've seen stranger things in fantasy to be sure.