What you shouldn’t publish on Steam: 15. Content that may violate the rules and standards set forth by Steam’s payment processors and related card networks and banks, or internet network providers. In particular, certain kinds of adult only content.
Payment processors calling the shots. Makes me think of that whole thing from the whitepaper...
What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party.