Not the nicest way to put it, perhaps, but it sums up the issue...
Carrying a backback, or a heavy shoulder bag, can hurt one's shoulders. Part of it is the weight, part of it is the way the muscles are used to carry it.
Braces hang from the shoulders. There's hardly any weight to support.
And if you decide to make a "package" joke, put it where it belongs - on the "Any Lovers of the Organ?" thread...