Sorry to bust the APS bra strap research committee before they even get started.
I see what you did there! And I laughed.
It's either that or the 'duty cycle' of the elastic in a bra is different than a waistband.
i.e. repetitive jiggle wear is harsher than static stretch.
Also, a few years ago I took Doggy Mommy (not to be confused with "Bitch") to a boutique known for fitting bras and catering to the local showgirls. Did wonders for her.