"Apple Pay doesn’t replace In-App Purchases. You should use Apple Pay when charging for physical goods (such as groceries, clothing, and appliances) or for services (such as club memberships, hotel reservations, and tickets for events). You should continue to use In-App Purchases to charge for virtual goods such as premium content in your app." Anyone understand why this is? Is there a reason I shouldn't let my users…
In think it more or less comes down to this: If you buy something you (potentially) use inside the app (an ebook, access to some server-side service you can use with the app, …) it’s an in-app purchase. If what you buy is something you use outside the app (a taxi, a pizza, all physical goods, …) you can use Apple Pay.
This differentiation has always existed. Until now Apple just didn’t offer any help with payment with the second category and you had to do it all on your own.