Please be honest. No one is that dumb, especially not you. The reason Japan's streets are clean is that they are used primarily by the Japanese. They have different cultural defaults than we do, and perhaps one might say that in this respect they are just better. Japan's cops are actually drastically less aggressive and abusive than USA cops. Also, numerous Japanese have told me that they wished their drug prohibition could be repealed. If that happened, no one would expect Ginza to turn into the Tenderloin.