The biggest impact crypto currencies will make is replacing fiat. With crypto, there's a reliable inflation schedule that we can count on ad agree to when we use it. With fiat, there's banks with presses that can print it any day they please as much as they like. With crypto, it's well known why people are rewarded new currency, and agreed upon. With fiat, those with the presses just give it to their friends and spend it on whatever they like.