What's possible in theory and what's possible in America are never the same thing.
Keep in mind that under any American model of legalization, there would still be plenty of people convicted of a crime for selling, buying or growing. The laws will be in place to protect the business interest and the interests of The Man. People would grow their own because it's cheaper, it's tastier, and the taxes that they'll levy on it will be insane. Those people would have to be eliminated. At $50 an ounce, the Cali tax proposal, there still would have been a huge black market, which means tons of people getting racked up on charges probably more severe than just possession of a dime bag.
I agree with you that we shouldn't even have to be discussing this, but at the moment, the current trend of low-profile, user friendly initiatives are really the best possible outcome.