Basically somebody somewhere just dreamed up some cultural thing where you're supposed to bathe all the time and expect it of other people too but if you think about it objectively it really makes no sense.
Indoor plumbing has only been a common thing extremely recently in the grand scheme of human existence and some places in this country it hasn't even been a thing for 100 years yet, and we're a rich developed nation, doing better than a lot of places in the world.
To think you must bathe all the time is the height of foolishness, yet people demand it to the point they scorn those who don't.
Ridiculousness I say.