My AP Psych teacher from high school keeps binders and notebooks with dicks drawn on them to use as visual aids for the Freudian unit.
One time she did this life changing little “experiment” where she ever so calmly asked guys why they draw penises on things. They tried to say “it’s just funny” or “you don’t understand” and she just kept saying “you’re right, I don’t understand. Explain to me. You already know what a penis looks like, why do you have to draw it on things? Are you marking it? Are you tagging it? Girls don’t draw vaginas on things.” And the guys suddenly started questioning their motives for everything they do and one guy was like “ms, stop talking about penises, you’re making us uncomfortable.” And she shouted “HOW DO YOU THINK WE FEEL SEEING DICKS DRAWN ON STUFF ALL THE TIME?”
In high school, I never quite understood why some guys did this (I was not among that group).