Europeans practiced excessive cash-based tax avoidance for decades before the euro arrived. When forced to exchange their paper currencies, lira, francs, and pesetas, bundles of cash emerged in suitcases to buy other cash-generating assets like real estate.
The irony of it all is that today the €500 note is the currency note of choice for money launderers because of its large denomination (the 1000 Swiss franc note is more valuable but it is nowhere near as ubiquitous as the euro note). As Guy points out:
The euro was easier to launder with banks around the world than the individual currencies it replaced.
Guy also refers to the dangers of a cashless society, but that argument has been made far more eloquently and persuasively by Scott Garrett. The more I think about these issues, the more I think that cryptocurrencies must be a critical element of a modern monetary system in a democratic society.