Just to be clear here (and this fact doesn't really detract from your point) - Apple Pay is very different to Apple's In App Purchases. Apple Pay can be used anyhere, and it could still be used if a company rolls their own purchase system on their website that they link to from the app. Apple only gets a very minor % cut of Apple Pay transactions, from the bank, compared to Apple IAP where Apple gets 30% from the developer.
Besides, isn't the competition here what we want? Apple IAP are still easier, and probably will convert at a higher rate than pushing a user outside the app to do the payment on a website, so there's still incentives for developers to use them. If Apps switch away from IAP, then Apple is incentivised to actually compete (imagine that!!) and make something better that developers actively want to use.
It says something about the state of competition where Netflix can just say "no, we no longer want people to sign up on an iPhone and give us money". That says they don't think IAP is good, and Apple should actually work on building something that companies want to use.