Yeah, kinda stupid if you ask me. But, I can understand the reason behind it.
Funny story, I joined the PS+ "family" once before. And I assumed my subscription would run out by the time the 3 month period ended. But, my subscription RE-NEWED itself, and I was forced to pay for an additional 3 months. That's where they get you.
It wasn't until I accessed my Account Management settings, put in my password and went to a certain sub-section that stated it would renew the subscription after the deadline. They expect everyone to access those specific settings and un-check the renewal box (or whatever it was) in order to automatically cancel the subscription, once the 3 month period ends.
Dick. Move. Sony.