A bit of a product marketing snafu by Apple if I may say. 1. Apple Cash is apparently not cash, nor a wallet, but a card that is stored inside wallet. 2.There is already Apple Wallet, Apple Pay, Apple Card. It looks to me that they're all the same. Why can't I Pay with the Cash in my Wallet. Or can I?
So Apple Pay is the service, Apple Card is their credit card and Apple Cash is their debit card via some bank. You can sidestep all that and just put your own credit card in the Wallet and use some other cash-like service.
The large problem with a lot of these cash-like services is in order for the exchange to happen, two people have to be on the same service. If Apple Cash takes off, then you just need to know if your friend has an iPhone and then its viable and much easier than having to go signup for one of these other services (zelle, cash app, venmo, etc.) just to chip in for a gift or dinner.