This is all Apple's fault for demanding 30% of their revenue from IAP.
> subscribe in a way that Apple has no control over
What is the benefit of Apple's control, though? That is the main question.
> I fail to see how this is not user error
It was user error. It's a very common user error, forgetting to cancel a trial. You're missing the larger picture here, which is that Apple publicizes and justifies its App Store lockdown and cut in terms of consumer protection, claiming that App Store is a very safe place to find and buy apps. If Apple cared about protecting consumers, it would protect them from common errors such as forgetting to cancel a trial. After all, Apple does "protect" consumers from the common error of installing software that they shouldn't from the internet, by completely banning internet app installs on iOS.