https://www.psychologytoday.com/blog/women-who-stray/201602/why-men-send-pics-their-junk
Aside from here, I've not gotten unsolicited peen pix.
The article tries to explain the motivation, and why it falls, um, short.
It got me thinking, and I'd rather see the whole picture. I want to see my partner's pleasure, on his face.
Another interesting point was "pre-approval."
Better to be turned down when not in the same room?
Yeah the article does seem reasonable, but it does miss a few obvious (at least to me) points, too.
I think guy who send unsolicited pics, in addition to what the article discusses fall into (but not limited to) one or more of these:
1. Validation of their size and ego: This goes beyond simple exhibitionism. Guys like this either do have large penises, or think they do. They send pics to get a response from a woman of "wow, you are so huge!" That ego boost alone is what they are after. The flip side to that is guys with below average penis sizes, that want an ego boost, and they want to have a response from a woman assuring them their penis isn't that small, looks OK, etc.
2. The fantasy: some guys send dick pics because of the fantasy of a woman seeing it, and "having to have it."
3. Weeny waggery: again beyond exhibitionism, there are just some guys who have a compulsion to show others their penis. Now that laws have cracked down (thankfully) on flashers, etc, sending a random text, snap chat, or email of their penis is the next best thing.
4. Intimidation or intentional harassment: Some guys send a penis pic with the full intent knowing it is unwanted, with the sole intent of harassing someone, or even intimidating them. It could be along the lines of wanting to intentionally disgust a woman, a primal way of saying "i'm the boss because I have the biggest wang," to something more nefarious as to imply they have a penis that could be used to hurt in some way.