Here's the deal: we all know what toilets are for. It's like the reason your parents close the bedroom door. You know what's going on in there, if you ask point-blank they'll give you a euphemism-laden explanation, but nobody really wants to have to think about it. AND IF YOU DO, FOR THE LOVE OF GOD, DON'T TELL ME.
We have this whole societal thing about toilets being in their own room, and in public places in their own room-within-a-room specifically to close off what happens in there from the rest of life so that we can not think about it, even though we know full well what's going on.
Or do we?
We think we know. We know what's supposed to be going on. But nothing could prepare me for stepping into the cubicle and finding tire tread marks on the seat AND bowl.