This question reminds me of a dog show I was at once. All the dogs were lined up on their down-stays with the owners 30 feet away. One very well-endowed male dog lifted his hind leg and began licking himself.
The very perturbed wife of the owner was standing outside the ring and she (not being a "dog person") said, "Why does he ALWAYS do that?" We all looked at her and replied in unison, "Because he can!"
I agree with Irme, it's a good thing that humans can't do that, the mortification index amongst the females of the species would skyrocket.