Underwear smell like poop

I'm a boy and wear boxers that don't smell but everytime I see an Instagram model in a thong/thong bikini all I can think of is how much the fabric near their anus must wreak of poop.

Most girls I speak of have big tushies and eat meat, they also most importantly are from America so their buttholes aren't that clean to begin with (compared to most countries that clean with water after pooping)

With all these factors the conclusion is they either wear these skimpy outfits once, or have closets full of poopy smelling fabric.