If you've ever tried to cancel Amazon Prime through amazon.com, you'll understand the value that Apple provides through its App Store subscriptions.
It is super easy to cancel Amazon Prime in the EU (I did it in Portugal).
Maybe we should expand it then? Make a rule that all subscription services shall to use Apple's iStore – it is after all the simplest possible way.
I have not cancelled anything on the Apple store, no. I have not yet had the burden of owning an iPhone, but I have cancelled a lot of things elsewhere. And the only situations where it has been anxiety provoking has been for US companies.
I sincerely feel sorry for you and how fucked up it is to cancel subscriptions in places with weaker customer protection.