Cash is king, no doubt but I am not sure it will still be king in 20 years from now. One of the reasons why small businesses still use cash is because it is available. If cash goes scarce as a result of facing a cashless economy, small businesses will be forced to add the 0.20% or 0.40% (depending on the institution and country) to the price of their goods and services. Over the last 5 years we have seen tremendous increase in cashless activities and we will surely see more in decades to come.