Blueskies you're on to something.
And I don't know about anyone else, but the skin around my chest, under the breasts is SENSITIVE. don't want metal wires digging in there; don't want scratchy fabric in there either. I mean, it's a light layer of skin that is sitting on ribs for crying out loud.
It's a trick to hold the weight and not abrade the skin.
and something like wool...

nothing worse than wearing nice breathable wool or whatever jerseys are made of everywhere except the bra, where it's cold wet and clammy...