Dunno how anyone could be perplexed ... piss smells like piss.
If you have 0 ideas about what it is, and piss seems improbable, I could see the confusion
Or expose it to warm temps in a lot of industrial processes?
It's a distinction without meaning, urea based products like DEF end up smelling like pee/ammonia. Laypeople usually specifically compare it to a cow urine smell