Saves money on incarceration, courts and police time. A new source of revenue for state taxation when the distribution network is set up. Conservatives often hate this kind of thing. They are always griping about making state government more efficient, but they (stereo typing on my part) oppose so many things that can put the fiscal house in order. Of course the Libertarians tend to be happy with this kind of thing and Libertarians can be found on both the left and the right of the political aisle as well as other spots on and off the chart.
I'm not a libertarian either, but would most likely call myself a maverick who tends to lean liberal. I just see hypocrisy in a lot of conservative efforts to balance state budgets. More states should try legalization of pot and so should the feds; and I don't smoke pot either; or at least very seldom, if I do.