"It doesn't make sense to charge for access to code or content, because it's not that too many people are consuming the good itself. It's the production—not consumption—of [content] that suffers from too much demand."

- Nadia Eghbal

Nothing stops you, but nothing stops you now. People could do that with the smbc comics. But the websites could have a "pay to remove ads" option.

Also, if there is a link to the article, there will be some amount of people who will pay the lightning invoice, if only to support the creator.