Interestingly, wearing bra's is not a healthy thing to do, and it has been scientifically proven that women who wore less bra's were less prone to experiencing breast cancer. In fact, in this study they have analysed thousands of african ladies living in tribes, where they obviously don't wear bra's - there was not a single case of breast cancer among them. Keep in mind that the study was huge, so this is a significant result.
Therefore, ordinary bra's are meant only for estetics, but it is not a healthy thing to wear them all the time.