The in-app purchase system is the one which takes a fee, and is only sometimes required (and only _usable_) for services or digital goods consumed in the app it

The in-app purchase system is the one which takes a fee, and is only sometimes required (and only _usable_) for services or digital goods consumed in the app itself. Any real world good or service would fall onto Apple Pay, which makes its money through a micro fee on the card issuer, basically to use the phone as a convenient, highly fraud-resistant card.