I can understand some people may not be shy. Modesty of one's body is mostly a social construct, I think. But it's not like these men walk about without wearing any... bottoms. They wear pants right down to their ankles. Yet they are okay with taking out their genitals and shaking them right in the middle of the street?
I discussed this with the Guy, but he has no idea either, never having had that kinda urge himself.
Do you have an answer?