Fees are negligible if you move to a L2 (even on L1s like Solana). Crypto is also permissionless and spending can be easily controled via smart contracts

Permissionless doesn't mean much if it's not anonymous (central authority wants to stop you from doing x; sees you doing x with non-anonymous coin, punishes you).

I understand the appeal of anonymous currencies like Monero (hence why they are banned from exchanges), but beyond that I don't see much use for crypto

Literally described the use case - a medium of exchange between agentic entities at massive global scale

Yeah, but doing it with non-anonymous crypto just seems worse in every way than doing it with a database?

Fail to see how you can do it with a database with existing financial rails - the costs are too high

All the same financial rails apply to crypto - enforcement is just lagging a bit.

E.g., you could do what World of Warcraft does - Gold can be earned/exchanged in game, and can also interact with the real world in nebulous ways. Using the hyper advanced technologies of relational databases and ignoring financial legislation, they have enabled ultra-high-throughput microtransactions, with the added benefit of not spraying the public ledger on to the desk of every law enforcement agency on the planet.