It might have to do with the fact that most states allow concealed carrying of hand guns now. There are millions of armed citizens and the criminals don't know who they are. As they say: More guns = Less crime.
Here in Michigan, there are pot stores everywhere. Almost anyone is allowed to grow it at home, so there is a booming industry in growing equipment. Almost every little hardware store sells the gear for growing indoors. Anyone with a card can grow up to 12 plants for themselves and carry up to 2.5 ounces on their person. There is so much good locally grown weed here that it's hard to find any from Mexico.