Laura Norén dives into the sociology:
Urination is a biological function that has been subjected to a great degree of social control. Unfortunately, urban design has not kept pace with the demand for clean, easily accessible public restrooms for humans. And there has been no attempt to create any kind of system to deal with canine urine. In most cities it is illegal for humans to pee in public but both legal and widely accepted for dogs to pee where ever they like (in New York, they cannot pee on the grass in parks). ...
One of the odd side effects of the introduction of the new TSA pat down procedures is that it revealed just how many people struggle with incontinence, either needing to urinate frequently or needing to wear diapers (or both). I was aware of those issues before the TSA started sticking their hands in private places, but I wasn’t sure how to simultaneously think about adult diapers, dogs peeing on the street, and taxi/truck drivers peeing in jugs while still in their cabs. Where social control is very strong as it is in the case of urination it can almost trump biological needs, especially if the biological needs offer a level of control.
(Hat tip: Flowing Data)