Provide a deterrent? I am sorry but I cannot agree. Companies will always choose survival over going bankrupt and closing down and that's basically what happens when you can't pay people. Users moving out to other platform will just make that one be next target in the future once it gets big enough, that's buying time more than anything. If payment processors and card companies mandated what can be sold with their services before, next will fall in the line because hosting content isn't a charity. Itch.io saved their asses first like any company would do, because NSFW content ain't the only thing they have to worry about.