You never have to charge your cash for it be useable, nor wait for the system update to complete to use it, nor hope for a connection to get to it. It doesn’t take a tap to use it or a slide. It doesn’t require software to choose from to use it. You can drop cash and it doesn’t break. You can sit on cash, get it wet, soak it and it’s still useful. You can pass cash from one person to the next nearly undetected by others. Cash is rarely traceable and it carries no transactions associated with it. I could throw up on cash, wash and dry it and still use it. I can crupple it up, have Fido fetch it and still use it. I can drop it off a skyrise and it’ll still be useful once found somewhere later on the ground. I can bury it for years and it likely will still be useful. It can get torn, discolored, have permanent writing on it and it will still be useful or can turned in for a replacement.
Cash transations with cash is easier for bunches of transactions that don’t need a bank account or access to a software bank or vault.