Using Bitcoin to trade doesn't make any more sense than using Google or Apple stocks to trade (with the difference that Google and Apple stocks fluctuate less rapidly in value). Oh, and the state-controlled water companies and the mostly state-controlled electricity company of Greece () accept payment only in Euros. And the special tax on all fuels (heating diesel, vehicle diesel, gasoline, LPG and CNG), which is seperate from VAT, is paid in Euro only, so gas stations have to charge in Euro. Even in if everyone else decides to sell you stuff Bitcoin, you still have to use Euros to live. BTW, if a country's currency become worthless (like a new Drachma will be), people typically use US dollars (see Zimbabwe), not obscure libertarian cryptocurrencies. Sorry.