The brute's, gone but somehow forgotten?

I'm not sure the correct lore on this but after the halo 3 incident, the brutes were removed from the covenant through some means... And 343, the game company, removed the brutes from halo 4 all together, yet the gravity hammer, a weapon used soley by the brutes, remains in the game, halo 4. In the campaign, the grav hammer is only seen once, at the end level, in some sort of weapon holding bay, along with some covenant carbines, battle rifles and so on and so forth. Why is it there though? Did anyone explain why? Is it just a remnant? Anyways, brutes have been removed from the game, and apparently the entire halo universe, as they are not mentioned again. Why?