Showing users nudity for free is fine. Making them pay for it means you're selling porn and the payment processors ban you.
Reddit wants to make users pay for viewing content. They can't get away with that if the content is NSFW.
Why can't that just be accounted for in the processor's rates?
People pretend their purchases are fraud or regret their purchase later so they chargeback more frequently than other services.
>Why can't that just be accounted for in the processor's rates?
Because it's easier as a credit card processor to just drop all of your high risk clients and focus on serving the rest of your customers as best as you can. Of course that leaves a whole in the market for other credit card processors that charge more for allowing higher risk purchasing.
This is the advertisers