Well towns could get away with it because they could rely on their farms and then every one would just revert to the old days. Cities though are such dramatic populations that they require so much supply and the only way to reel that in is by vehicle. Vehicles require gas, gas is imported by big corps which will NOT accept small time currency(especially considering how they are in on it).
What we need is a crazy energy source. I wonder how many people have been shot for discovering cold fusion. lol! I laugh and cry at this at the exact same time.