I am very chesty so going without a bra doesn't make sense for me, although I am lucky enough to be perky and I do have a dress I wear braless: it has the shape of a cup built into the bodice and actually looks better without a bra. The dress is a heavy pique cotton, so there is no see-through issue.
But for the women who are small-chested, I don't see any problems with going without. If you don't feel that you look better in a bra, what's the point? If there is an issue with nipples showing, there are "petals" that you can affix to your nipples to hide them.
Mamapicklejuice, I wouldn't want welts either. It sounds like you may have been mis-sized, because a properly fitting bra does not equal welts. If you just have a little bit of red marking for the first few days, that could be different, almost as you "break in" the bra. But if you have welts and the bra feels uncomfortable, it isn't fitting properly. I would go back and try more 32Cs and some 34Bs as well. Not all styles are the same, and I find that some 32s are too tight while others are too loose.