You may missing a point, your subscription you engage yourself by contract to keep for a year becomes a financial asset for the company which can then use it to get loans, raise their stock value, etc. etc.
If you can then reverse your engagement as you see fit, nothing holds anymore.
The part you're missing is that contracts like this are contracts of adhesion, and there may or may not even be an option to sign up one month at a time. And even if there is, having a penalty clause for canceling a contract is reasonable, but having a penalty clause that massively exceeds any plausible damages isn't, particularly when one of the parties in that contract has dramatically more power than the other, and that party is the one writing the contract and demanding the penalty clause. That's why it is reasonable for governments to limit the amount of those damages through statutes. It is just compensating for that inherent power imbalance.
Also, real-world companies aren't typically selling bonds against their subscription revenue, and unless this is a very small business and the contracts are among equals (which a customer relationship almost never is), a bank isn't going to care about the difference between 1,000 subscriptions and 1,001, nor do stockholders. They care about the difference between 1,000 and 100,000. Orders of magnitude matter. A few cancellations around the margins are noise. So although you might be correct in theory, in practice, single cancellations don't matter, and if the cancellation numbers are high enough to matter, there's something much more seriously wrong with the company, and locking consumers in to a long-term contract likely serves no one's best interests, including the company's, because that just reduces the pressure on the company to fix those structural problems.