Itch.io basically de-listed any sort of NSFW games from the store, people complained, then Itch.io magically found a spine and re-listed what was on the store, though the developer Nomax (who made the game called Conway) on Itch.io also commented the statement in a thread, "Conway and other NSFW games currently can't accept donations if we want to be visible on the site."
So it seems like Itch.io, the payment processors, or some combination of the two is fully intent on keeping NSFW works from making any kind of money.