Your hands are covered in bacteria, yes, but maybe you don't want them covered in the bacteria that eat wee.
if they dont make me ill, and don't smell they are welcome to my wee....
so wee on hands would change the bacteria population, or at least cause growth of a different population that was not already there?

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I also believe that people are over sanitised - however, hygiene is also done not only for cleanliness, but out of respect and environment of other people around you. I don't particularly want to touch other people's germs, spit, or urine. It's gross. Admittedly we all undoubtedly do so more than we realise.
I wasn't picking your post for that reason alone, just if anything trying to add to your points.