> You're buying an expensive entry in someone else's database

Nope, you're buying a non-fungible token on a public ledger where the data and association with a specific address (or addresses) can be read without permission. This ownership and permission can then be moved around (potentially for large sums - potentially for near-zero amounts) by means that are independent of the client used. So for instance an NFT could give me access to an exclusive Discord channel (the client here being a Discord bot) and I could potentially sell or otherwise pass that onto someone else who wants access. The ownership of that token could also afford me access to, for instance, buying another token on another smart contract (the client here being another smart contract).

That they are commonly linked to metadata associated with JPEGs is really missing the opportunity here.

Furthermore, since everything's on a public ledger the much-stated money laundering is surprisingly difficult. And in fact multiple people have been caught out by this (a simple example being one of OpenSea's PM's wallets showing that they were frontrunning; another is VCs front-running their portfolio companies' air drops). That NFTs are often exchanged between bot accounts and multiple wallets (often tracked back to known individuals) to pump prices is also well-known and visible on the blockchain.

Whether or not you think expensive JPEGs are 2020s' Beanie Babies, it's hard to imagine a programmer on HN not being able to think of interesting non-JPEG things to do with an open source, public and permissionless ledger/database.

EDIT: disclosure - I have some JPEG NFTs. They weren't super expensive to me but I bought them so I had skin in the game that forced me to investigate this market rather than shouting "but money laundering!" from the sidelines. I'm glad I did this. Via getting into the weeds I've discovered a vibrant and super interesting ecosystem of developers, entrepreneurs, cryptographers and opportunities I'd never have known about otherwise. Are my JPEGs worth it? Doubt it. But the experience has been super interesting so far.