Yeah, neither of those make sense to me. You can easily cancel netflix online and the last gym membership I just called and cancelled because I was moving. I've heard about gyms "requiring" you to cancel in person but I feel like a threaten to do a charge back would get them to cancel over the phone.

Why are people paying for subscriptions they don't use?

Laziness

Also excessive optimism. "I will finally start excercising next week, I swear!"

I mean I use my gym membership, but I think the analogy is wrong. People don't use their gym membership because it's just an office to do (body)work in. Netflix is entirely consumable for the purchaser, not much work involved. Laziness might still be the answer in common.