>The only real use case that makes sense to me...
Cryptocurrencies have a great and really boring application. You have to think "who needs a reliable ledger distributed among many entities?"
The answer is institutional banks the likes of JPMorgan. They have a few cryptocurrencies, you need to be another large bank to use them. Big banks send each other large sums of money constantly back and forth. In no sense do they send each other "real" money, it's just accounting... a ledger.
"Cryptocurrencies" are better thought of as mathematically proven accounting software than money. Plenty of organizations need to be able to keep track of money is between a collection of mostly-trusted peers. With cryptocurrencies they can ditch a lot of the transaction and accounting software.
But a regular database can do that with PKI. Crypto isn't just a reliable ledger -- it's a reliable ledger between an arbitrary number of mutually distrusting parties. Which doesn't really describe banks in a regulated, functioning economy.
What's your definition of a "regular" database? If you need a distributed, well-sequenced, auditable trail of cryptographically signed operations representing the transfer of value, that quite literally can be fit to match the definition of a blockchain.
People who haven't done it probably underestimate the incredible amount of fiddly nonsense is involved in actually writing accounting software to handle a ledger.
Banks and brokerages very often use software written 40 years ago because it's so much trouble to get correct.
Not that I don't agree, but PKI relies on a trusted authority which can be compromised. If you're running a trustless system, basically any party can be compromised but the blast radius is limited to just the compromised infrastructure and money, not the entire system.
No, a regular database can't do that "with PKI", you have to write ledger software on top of it and you have to have one party operating the software.
cryptocurrencies are the ledger software, API, and data store layer -- and you do need trust between peers because the JPMorgan will take actions to reverse transactions if there are problems that need fixing.
It's not magical, but it is convenient for the actual ledger actions to be mathematically proven instead of the result of accounting rules in code.
> In no sense do they send each other "real" money, it's just accounting... a ledger.
"Real money" these days is exactly that, i.e. accounting entries on a ledger, and has been for the better part of the past century or so.
> Plenty of organizations need to be able to keep track of money is between a collection of mostly-trusted peers. With cryptocurrencies they can ditch a lot of the transaction and accounting software.
What is blockchain technology if not even more complex accounting software? It has its uses, but a network of mostly trusted peers is probably not one of them.