Y U No Poo? Elements Left Out of Worldbuilding

Hygiene and basic bodily functions tend be glossed over in World Building...unless killing someone on the john is a plot point (hiya, GRRM). Rarely does our protagonist take time away from the action to brush their teeth, wash their hands, or pee. They only head to the loo when the setting of the bathroom is important (fist-fight, clandestine meeting, assassination, hiding from an assassination, etc.). Even then, it's only one potty visit for the whole novel. There are endless memes for 24: When Does Jack Bauer Pee (pretty sure Eric Carter's going to have the same problem, fwiw).

Anyone who has kids, a vindictive bladder, or a digestive system that functions like clockwork knows where the restrooms are and visits before jumping into the next adventure. Office, gas stations, Target, rest stops, port-a-pots at the farmer's market...real world logistics are planned around potties. In SFF worldbuilding? We'll send our fearless posse into the glacial canyon, covered in eighteen pelts of wild beasts they slaughtered and skinned with their own hands...and no one is concerned about copping a squat in sub-zero temperatures.

Or toilet paper. 

How many of our fearless heroes are running the gantlet with grungy butt?

We skip that shit (literally) because readers don't want to know, unless, again, it serves a plot point.

Now, showers, on the other hand, they are the literary stars of the bathroom. Giggity-giggity.