When people pee on them, it certainly doesn't help the situation.
That and among other crude practices...I once shined a UV flashlight around in a public restroom, well, all I can tell you is carry plenty of hand sanitizer.
I take one of those UV flashlights to motel rooms.
They seldom clean the bedspreads, unless you ask.
Not to mention the upholstery for the chairs/couches.
I too have seen hot spots on bedspreads and upholstery...and even on the walls while wondering, how the hill did biofluids get on the walls.