Apple isn't going to kill cash with
1. A Market share that fluctuates between 40% to 60% market share from generation to generation.
2. People who still use terms like "Davenport" and "Ice Box"
3. People who still use flip phones.
4. Anyone who doesn't want to be tracked.
I know several people who refuse to have cellular devices or bank cards because they would rather pay their bills in cash, or by converting cash into a money order and sending it.
As for digital payment services for brick-and-mortar stores, the only one I have ever liked was tied to the store's POS system, and didn't require me to screw around with my phone at the checkout to pay. I just put my finger on a reader, entered a pin, and used one of the payment methods I had previously stored in their system.