A hacky way to do it, I guess, would be for banks to make is really easy to spin up debit accounts. You drop exactly the right amount of money into the account, then when you want to unsubscribe just stop putting money there. I guess, though, some organizations would keep providing service and then consider you to owe them money, and eventually send it to collections... but if this was the conventional configuration for paying for accounts, I guess that sort of behavior on the part of the people looking for payments wouldn't be scalable, and so they'd have adjusted to just accepting the signal of non-payment=unsubscribe.
Lots of banks already provide this service (spin up as many unique debit cards through an app as you want), at least in Europe and Asia where I've used it. It's often marketed as being specifically for this purpose, along with extra features like locking a card to the specific merchant you plan to use it for, to guard against theft of the card number.
Are there often legal issues around not paying for services with annoying contracts? In the US it is not super uncommon to pay after consuming (this is how electricity typically works for example) or for services to offer some grace period where they'll keep providing service with the expectation that you'll pay back later. Hypothetically these companies could I guess sue you if you don't pay back later (I'm not sure actually -- more likely I guess they'd send it to collections). But if the default way to cancel a service was to just stop paying for it, then I guess companies would change how they billed (fundamentally I think paying beforehand would be more convenient for most consumers).
I accidentally dinged myself with a couple hundred dollar AWS bill -- surely nothing nightmarish compared to what others have gotten, but it sure was annoying.
Why is this still a thing?