Maybe in a different time, when boobs aren't seen as sexual. While they remain sexualized, you just shouldn't show them, just like men can't show their dicks.
If you take a step back and examine this logically, it quickly becomes apparent that we have no apparent reason at all to not allow people to walk around completely naked.
The reality is that we, as a society, arbitrarily chose a set of organs and labeled them as sexual. Not only "sex organs" like the penis or the vagina, but also stuff like assholes and breasts.
If you believe that we should aim to desexualize all body parts, I could get behind that.
If you don't, answer me this question: What possible harm could come from me walking around with my dick out that couldn't come from a woman walking around with her tits out?