Nipples..

So I'm kinda curious about this. It seems to the men I know that if a woman's nipples are hard, she's turned on. I feel like that just isn't true. For myself, I have never had hard nipples when I'm turned on, in the middle of sex, or climaxing. I only have hard nipples when I'm cold or its rubbed against my shirt or bra weird and is irritated. I'm just curious. Is this common in women? I've never asked my friends or seen it with the female partners I've been with, though I wasn't specifically looking for it. So my question is: is it common? Or just a stereotype that men create?