Decriminalizing marijuana would save a lot of taxpayer dollars currently used in the search and seizure of marijuana, prosecution of people charged with marijuana possession, and money spent keeping them in prison. Additionally, cannabis, the plant from which marijuana is derived, is a very diverse plant that can be used to make many things and, thus, a very profitable crop that could actually help the state make money.
There are many other more serious crimes that need attention than marijuana use. Many people who use cannibis aren't violent. Putting them in prison for such a minor thing end up costing the state thousands of dollars. Maybe the same rules could apply to marijuana as with alcohol : no selling to minors