Hi Sonzi,
Good Question! There are a few reasons , firstly I wear a wireless bra, under wire bras are uncomfortable with having less cushioning from double mastectomy .
I had radiation after stage one with the skin expanders in and before silicone implants , this left one breast slightly smaller than the other from skin shrinking over time.
This is why I mainly wear the bra to keep both breasts a similar shape as the non radiated breast will drop and stretch from gravity over time !
And then there's the added shaped that a bra gives as my implants are a 34b and my hips are 40 so the bra helps to add a bit more up top !
I hope this explains it ......
Kim