I don’t know who at Coinbase discerned that HTTP 402 is unused. There are sites that return 402 and a relevant “pay your bill to continue” page out there. Not all of them will suddenly support this blockchain payment method.

its not that 402 isn't used, its that there is no standard response, which makes it hard for AI agents to pay for access. x402 provides a standard response format clients can programmatically use to create a payment, either using crypto assets like stablecoins, or in future, fiat methods.