Piss is not sterile.
Analogy is not good, either. But kudos to anyone still trying to make it work.
Piss is also chock full of concentrated salts and metabolic waste that hasten dehydration. Drinking piss is definitely not an option.
Now you can take the piss and use evaporative distillation to extract the water from the mess, but that takes time and skill and know-how. It’s not as easy as, ya know, drinking piss.