I wrote USD, not cash. Most transactions in USD are electronic, not physical, so it’s a little unclear what point you’re trying to make.
Going even further, cryptcurrencies, being distrusted ledgers, still fulfill the ability to test for someone "social trust" within a transaction, anonymous or not. Also, it's not like we, as the whole society, have access to your transaction history at all times with USD (which we do with Bitcoin, funnily enough).