The argument I had originally heard was "the transaction costs of credit cards is so high, we need a system that works for many tiny payments. But of course, most of the cryptocurrency transaction fees are still pretty high, and a dedicated "tiny transaction" company would presumably be able to offer the same service for less cost than a distributed equivalent.

This sounds like a reflexive "I hate blockchain and cryptocurrency" reaction but I'll give a reply regardless.

You can't do transactions with just a database. You'd have to add a payment processor. Now things are getting wildly complex.

x402 is designed with agentic AIs in mind. AIs make mistakes. Having an immutable record that can't be tampered with is a nice layer of security.

And while I haven't worked with it personally, I understand x402 to be extremely straight forward for devs to implement.