I have heard the opposite - that bras do nothing to prevent the sag. So what - they fully hide it (good bras are great at that). Because in the end a TINY percentage of people would ever see me naked, right? For the rest - I have perfectly shaped breasts, thanks to the bras. So I am definitely not going to willingly give up this wondrous piece of clothing even though there is no respective equivalent of it in the male wardrobe.