Ok now I'm not sure which aspect you're talking about.
Because in the physical world the friction is not "oh I need a card" it's physically getting the customer in the door. Otherwise, what's involved is needing merchants to have NFC readers. This might be an exciting new thing in the US, but certainly in my neck of the woods NFC has near universal penetration.
In the virtual world...this problem has been solved over and over and over. I'd argue it would be very surprising to see Apple displace Paypal. Everyone has Paypal - very few people (relatively) will have ApplePay.