I’m a guy and I don’t understand that.

I’m a guy and I don’t understand that. However, I have to wonder if it has ever worked? Some woman on whatever app got a dick pic and was like “ON MY! I MUST get me some of that!” Of course, I’m joking because I simply can’t imagine that being effective…but what do I know. 
I’m not a prude, but that behavior really confounds me.
Fellas? REALLY?