Why are guys expected to wash there hands after going to the restroom to pee?

I've never understand this, seriously. I don't know about other guys but I don't piss all over my hands when I use the restroom. Now #2 i can understand the logic. But going to pee, i mean my unit is in my boxers protected all day, i don't touch it unless i have to pee. I mean my forearms see more exposure to germs in the day wearing a short sleeve shirt than my unit does, what gives?