Apple Pay can't just charge the credit card on file with iTunes because Apple doesn't actually store bare card numbers for Apple Pay payments. They use the card

Apple Pay can't just charge the credit card on file with iTunes because Apple doesn't actually store bare card numbers for Apple Pay payments. They use the card number you input to access the provider's network and get a token, which they then use to actually make transactions. The provider has to have agreed to integrate with Apple's systems to generate those tokens. They have a good write-up of how the system works here: https://support.apple.com/en-us/HT203027 https://support.apple.com/en-us/HT203027 Key part: > Again, neither Apple nor your device sends your actual payment card number. Before they approve the payment, your bank, card issuer, or payment network can verify your payment information by checking the dynamic security code to make sure that it’s unique and tied to your device. Apple Pay requires tight integration with the actual Provider of your card to authorize every transaction. For contrast, Samsung Pay works by sending the bare card number to card-reader device by emulating magnetic fields. It's exactly as if you swiped the card, which is why it works with almost every card, and almost every card reader. It doesn't have any of the security benefits or guarantees of Apple/Android Pay, though.