Psychology 101:

People sign up for just a month. Don't cancel immediately after watching the movie they want, because they want to use the paid month in full. After two/three weeks the brain phases out the expiration date and the subscription renews.

"But reminders!" the reader would complain so let me preempt that: not many person actually set reminders for this kind of stuff - part because 'it's only a month' part because not everyone is as phone dependent as techhies and mbas types. For internet and social? Sure. For reminding every little detail in life? Hardly. Especially since outside apple setting a reminder is still a subpar experience.