We are going toward a cashless society.
What's the problem with electronic banking and plastic currency -- governments can account for and tax all your income?
EBT cards are electronic now. Government payments are ACH direct debit.
People not evading taxes are not inconvenienced. The government would start an armed rebellion if they confiscated citizens' stored currency. We would have 100 million armed lunatics in the USA
10% to 20% of all the transactions in the US are in cash and 'under-the-table.'
This taxation capture in theory should lower overall taxes but it probably will not.
I carry less than $100 in cash normally for incidental purchases -- and a lot in plastic.