Currency as a protocol or data structure that exists in the same world as code and applications.

Especially with lightning transactions, you can treat money like a value in a redis cache but it's on a consensus layer that exists beyond your application and not a third-party service that could be shut down or have its prices/api changed.

For example if I have some program that generates some GAN image based on parameters sent by a user, my application could create an invoice that would need to be fulfilled for the user to get a result. If you aren't using bitcoin, you need to go through something like stripe or paypal and need to consider certain regulations, apis, and user payment friction. But if the application logic is just "server generates invoice > user pays invoice and POSTs parameters > server computes > server sends results" this can happen entirely without needing to pay some payment SaaS or considering what country someone is in or what currency they have or payment providers they have access to.

Another example could be a community minecraft server. You could set up your server hosting provider to get payments via generated invoices from a bitcoin address. When the address has less money than the monthly payment, it could broadcast a message to users that the server will shut down X days unless the address gets enough funds. Players can send money to the address until it reaches the quota. Especially with more normie-friendly apps like Cashapp allowing bitcoin/lightning transactions, it's becoming more and more user-friendly. This can all be programmed in some java plugin on the server and the server operator doesn't really need to consider payments since the users are using the service and should be paying for it.

Things obviously get more complicated if you have enterprise SLAs, if you are a business with strict GAAP and tax requirements, do business with many actors in b2b or high-regulatory environment, have users in countries where crypto is outlawed.... but I think bitcoin/lightning shines with small internet utilities like bots, web services, or game servers.