Most currencies are digital now but currencies like the USD are centralized and can be created non stop with little effort. The majority of cryptocurrencies are decentralized and have a cap on the number of coins minted and they are created by using electricity and hardware. Lots of labor had to be done to acquire the materials to manufacture all the devices that make up the cryptocurrency networks. Now anyone can have their own digital printing press and can even create their own currency instead of that kind of power only being in the hands of a few.