There are places in the world where people still use natural resources more than fiat currencies to transact. In Sub-Saharan Africa a grandmother will grow a crop of tomatoes to trade for two chickens and 40kg of rice. She will earn 1.50$ per day otherwise. It would be great for her to use e-cash to make those transactions, But a 100$ smartphone is a serious investment for an elderly woman who relies on her 8 grandchildren to help her along in life. I am just stating it is worth doing some market research to find real world use cases.