If the Greeks had been doing this all along, they would not have many of the problems that they have now. It’s well-known to European vacationers to being cash to Greece because you will get a better deal on anything. Greece effectively has two major economies.
I’m one of those “European vacationers” and was last in Greece in October. No, you do not “get a better deal on anything” by using cash (to any extent beyond any advantage here in the states).