"Large Penis Humiliation" is an odd concept, but it makes sense that in a world where you can be anything, choosing an overly large penis would get someone to think you were compensating for something.
It humorously inverts the relationship between the penis, and the act of projecting strength to make up for what you lack.
Instead of seeing a man with a sports car and thinking his dick must be tiny, you see a wolf with a horsecock too big to fit into anyone and laugh at how insecure he must be as a man to choose this form, and what a gooner he must be to have a penis that can only be masturbated without ever copulating. It's not just rejecting the wolf form, it's rejecting the function of a penis, it's rejecting togetherness so he can lean forwards and hug his body pillow-sized cock as it ejaculates. In a world where you can be anything like VR Chat or a world of shapeshifting furries or shapeshifting magic/nanomachines/drugs, a choice like this is cringe.
In a world of furry animals, getting a giant boner in public might make characters see you as "lesser" and "more animal than person" and "less of a person and more of a sex object".
Bragging about the dick size of your Dungeons and Dragons character is cringe but forcing the party to deal with the problems and stat penalties that come with having an excessively oversized cock is worse. There's a point where "What a hilarious joke character" becomes "dude, seriously, again?". So if you're doing that thing comics do where sometimes you see the players and sometimes you see the characters, that could work.
But instead most large penis humiliation art is just characters acting like huge is cringe and bad for no real reason.
Why is that?