Your post reminded me of Ben Winter’s last book in the Last Policemen series. The hero is riding around on his bicycle through a pre-apocolyptic, collapsed society and comes up with a system for coding the state of towns he rides through. Some have devolved into violence and chaos (red towns), some are peppers hiding behind walls (blue towns), and some are “make believe” towns where people have decided to just carry on with civil society, schooling children, growing crops. These towns are obvious because they all still have trash collection. He says, “Wherever we see curbs free of trash, or people bringing their waste to a collection center, people going out of their way for the common good, we know it’s safe to sleep there.” The idea seems to fit here.
Excellent example of an illogical and possibly harmful cultural norm that we Westerners can understand. Our (US) whole custom of putting the place where you defecate in the same room where you’re meant to clean your body is kind of counterintuitive. I get that it probably evolved for ease of plumbing, but most people don’t even question it.
Side note - the Indian habit of al fresco pooping probably avoids people developing that weird quirk where they have to get totally naked in order to poop. 
