Apple has control over which apps they allow. Even with alternate payment methods they can still enforce 1 click cancel, they just don't want to because money.
You are right, and of course there is not always a surcharge. I myself am a big fan of easy it is to cancel when using Apple Subscriptions. However, there are tons of online services that WILL charge your a significantly higher subscription fee, when using Apple Pay (Tinder is a prominent one).
When I'm signing up for some streaming service to watch one or two shows and know I'll be done in a few months, I have no problem with the 30% surcharge. It's paying a little bit more now to make things easier on myself in the future.
It’s 1 click cancel on subscriptions.
It’s enforced and they have no say or cannot make it difficult for me to cancel.