Dogs socialize by scent.
Much like my 9 year old neighbor marked her territory on the hydrant across the street with dozens of leftover bottles of nail polish, so too do canines drip potent liquid on the metal torso that enables fire hoses in emergencies.
Such piss tells every other dog that cares to sniff just how hydrated another dog was, what they ate, how long their human counterpart allowed them to relieve their bladders; was it a quick “GOTTA RUN, HAD A RIB,” or could the pooch pee particular pieces providing passionate portrayals pushing peons putting past pups ?