Imagine the situation in which we don't have any physical money and every currency is digitalized. The US dollar is now a token, the Japanese Yen is only in the network and the British pound is a fast-moving digital coin. What are the consequences of such an economy for the poorest of the population? Do you think that a few people can influence the digital wealth of people and wouldn't hackers be the best people to have as friends?
An economy without physical money is something of the future, unless and until the complete living population is able to adopt a digital payment setup, this future cannot be realized.
This complete population includes both the rich and the poor, however, the rich with access to more resources can stay above the curve with more knowledge of technology and a better way to make the new tech work for them. The poor on the other side often lack technological literacy to fathom the intricacies of a new advance system. So they may take more time to adapt. Having said that, this doesn't mean it would be bad for the poor. If digital currency is made mainstream, the rich don't be able to get away with tax evasion and other illegal monetory transaction, this will keep more money flowing in the economy which will help everyone in the long run