One problem that may hinder a cashless world involves identification cards that those people in the lowest social class do not have. To be capable of getting valid wallets (digital form, probably on phones) or card (in physical form), whatsoever, ofcourse, you need to have an ID. KYC is one proof that only those people in the middle class and above can be involved in thos kind of community. What about the poor ones? They won't be able to afford getting cards etc because most of the time they do not have valid ids. Probably maybe because they don't have work or money to produce one.