That is just not true. Like I mentioned up thread, I’ve lost a huge amount of weight and have very deflated and saggy breasts, my breasts naturally rest around 6in below the inframammary fold which is the most severe kind of breast ptosis (sagging), my nipples point downwards and rest around 1in above my belly button. The breast tissue is in the bottom of the breast near the nipple, and the rest is skin. At the point where my cleavage should be, my chest wall/ribs protrude out further than the breasts themselves. Again, the skin is thin and crepey, and is just a mass of creased skin when encased in a see through bra.
BUT, the majority of the support still comes from the back band, despite my breasts having absolutely ZERO ability to hold themselves up, it has to come from the band. Relying on straps alone with a loose back band creates a pendulous effect when you walk and is not supportive enough, the shoulders are welted, the breast tissue further migrates around the sides, etc and it just doesn’t work or create a pleasing appearance in clothes.
A lot of people are uncomfortable with a very firm bra band, but it is 100% necessary for the best support, lift and back/shoulder health.
(I have all this detailed knowledge of breast sagging as I’m booked for a breast lift soon).