You’re pathetically naive if you think that gangs and illegal commerce in pot will just “go away” with its legalization.
Look at the Alaska pot law. Of course it will. You can grow your own plants and smoke in your own residence. Why pay for what you can grow for free. That would be stupid. Pot is a ‘weed’ and can grow anywhere, really. Besides, where would the massive illegal market be if you could grow pot legally and buy it legally.