Can you imagine a man enjoying getting an unsolicited picture of a naked woman?
Personally, I don't like it. But women send them... because they assume men like them. And even though I don't like them, it does cause me to think about the woman who sent it.
And people want attention. Often they are so desperate for attention they will take negative attention. Just to feel seen. They want to be thought about. They want to be sexualized.
There are tons of easy reasons people do it. Some better than others. But it makes sense why it happens. One positive response, and you're probably putting up with a thousand negative responses in hopes you get a positive response again.
In my own limited experience of receiving that sort of unsolicited "art." Even though I don't like it. The people who send it to me, do, on average, end up getting laid. Too me, it's despite that behavior. But who knows what they think the cause and effect is. And maybe I'm fooling myself.
Because even though it makes me feel uncomfortable, it does sear itself into my brain. Pretty permanently.