If you were able to do so would the result not be the same. We dont accept your terms update so we and terminating your subscription. Essentially the same that you can do.
You'd have to elect to resubscribe with the new terms. Bonus points if it has to be the normal subscription flow, not some kind of one click to resubscribe.
I'd bet the pressure of instant drop in revenue and the likelihood of people being less motivated to resubscribe would kill some of this behavior.