Even the most simulationist game doesn't need to simulate elements that are covered in a fictional tale about the same genre in a few lines, if not ignored entirely.

You don't need rules for how often you have to stop for a potty break in D&D because it's just assumed you do when you need to, and that you can hold it when it's not convenient. In a game about long road trips where every second spent stopped is a hazard in its own right (perhaps a race across the country for a treasure or across the world for fabulous reality TV prizes), keeping track of the bladders of one's passengers may actually be relevant.

In D&D, if for some reason it did become relevant, the module would either provide some one-off rules, or the DM would likely assign a Constitution check to "hold it" after a certain point made it plot-relevant.

(I actually had a DM do this in X-Crawl: we'd been given tacos in the green room, and they...weren't the highest-quality meat. Since voluntarily leaving the Crawl removes you from your team for the rest of it, and all the restrooms were outside the exit doors...)