A legal product can be regulated and taxed. A product that's completely illegal can't. It could be like alcohol, where you have to sell it in certified establishments and can't sell above a certain quantity to a person at a time. It would if anything produce safer smoking behavior. It would also produce revenue (again, the tax thing) rather than draining revenue with all the effort spent to arrest and imprison huge amounts of people, many of whom have no other crime on their record besides marijuana possession.

I would never smoke anything myself, but it still doesn't make any sense to me that it hasn't been legalized. Banning alcohol did not work, and banning marijuana hasn't worked either, so why not scrap the ban?