Hard point to argue.
If the person that frequents your shop, doesn't have the currency, why should I accept it.
Kinda Egg or Chicken problem tbh.
I feel BCH has a leg up in this regard. We give away BCH freely, so others can use it, try it and decide for themselves.
It's easy to use and accessible.
If there's an easy on/off-ramp and a good (beside Bitcoin.com) Smartphone wallet, E-Cash could become reality.