Yeah, my comment was based on that hardness is called out specifically as a quality of objects, but not as a quality of creatures.
as we all know, D&D is the game of exceptions to the exceptions of the rule, so obviously there are creatures which do have hardness - though they do tend to be "object-like" most of the time.
not to mention that armor and shields have hardness, but neither subtracts anything from the damage you take. hardness only comes into play with shields when you try to sunder them... and note that technically you can't sunder armor somehow....