Gaylene's got a good point. It's a feminist issue.
Seems to me there are some women who just can't "smooth away" their nipples, no matter how padded the bra. For this reason alone we should learn not to think of visible nipples as "distracting". They just are what they are. News flash: women have nipples!
Janet, I know what you're saying. (Nice imagery, btw, lol). I'm already aware of my boobage, and if I had prominent nipples, I'd probably try to conceal them. Or maybe I wouldn't. I really don't like the feel of padded bras. And I'm not opposed to the idea of nipples being visible. But as it is, mine never show through clothes (unless it's below freezing), even in the thinnest, stretchiest bras.