I believe it is an empirical observation made by our pre-bra forefathers upon seeing how breasts cooped up for decades in the "over the shoulder boulder holder" would sink like stones when the bra was removed, to a degree that breasts from the more free-hanging era did not. Probably the only good thing that feminism ever did was discourage bra use, and of course that's the only part of feminism that women didn't embrace. Besides, it's a fact that the corset is more alluring. The corset is also a dietary aid, and a superior support garment, as bras definitely induce back pain...and faggot butchers masquerading as surgeons are all too happy to relieve that pain from endowed women via breast reduction surgery.