No batteries
At least neither cash nor plastic need a charged battery - with cash also not needing a working network to accept the transaction, a problem in some areas. So some people feel happier having more options available. Dealing with trivial payments via some form of month end account can be a real pain for many. I understand that for others it may just as well be an asset to have an electronic record. Some of us remember the days when just one card type might be accepted - never the one you had at the time and painful memories can linger on.
I have no down on anyone using their method of choice, I embrace empowered choice. Compulsion is different thing and that is the one I hate, almost as much as my wife hates 'SMART phones'. I have one it is smart enough to know I want to do something and frequently clever enough to stop me achieving the option in a timely manner. For me plastic and cash are rather easier and provide me with comfort.
Cashback was always said to provide comfort to the retailers who offered the function as it moved physical cash, which needed manual handling into an electronic form simplifying their book keeping.