This is something I think people miss. Almost every other company I have subscriptions with make them a pain to cancel. Subs through the App Store are easy to find and cancel. It's very consumer friendly. Plus as you said, I'm not a fan of giving every service I want to use my CC.
Is that worth 30%/15%? I don't know. The fact that 15% exists shows that Apple is thinking about the pricing and adjusting. Apple just doesn't do anything quickly.
It is impossible to stop the subscription. No thank you, I will trust my payments with Apple.. Esp. subscriptions.