That's true, but if you're on some (still ongoing) specially discounted monthly deal you don't expect to cancel yet after this month (as the OP indicated), you'll still need to wait to cancel. And sometimes, you might have a discounted offer that would expire as soon as you cancel and you're...
That wouldn't really help for keeping track of when to cancel/suspend (and/or reactivate) streaming subscriptions (whether because of some expiring deal or some other reasons).
Some of us are indeed juggling when best to do such, especially if we're only interested enough in particular services...