I've always wondered this. I use my urine diluted in water to feed my plants because of the vast amounts of nitrogen and phosphorous. Urine is naturally acidic, so it would seem to be a natural way to PH up along with adding trace minerals and nutes.
"PH UP- or potassium hydroxide PH DOWN- nitric acid, phosphoric acid, citric acid or vinegar" taken from Jorge Cervantes grower's bible. Urine is not listed.... and do you want to smoke a plant that has been drinking your piss? I'll pass on that joint.
So..
Bat Shit: Good
Cow Shit: Good
Horse Shit: Good
Seagull Shit: Good
...
...
Urine: Ewww disgusting?
Not that I personally plan on pissing on my plants, but I don't understand the problem. Though it would probably be better to piss in your super soil and let it "cook" some...