There are a lot of people who deal in marijuana who are very nasty people. They are willing to destroy property, hurt individuals, even kill and maim to protect their grows and or territory. It is very unlikely, were the drug to be fully legalized, that these nasty individuals would become productive valued members of society. Organized crime did not go legit just because prohibition was repealed. It is funny how people are willing to boycott corporations for perceived wrongful practices, but few if any will forego their drugs to affect the nasty growers or dealers.
That may be the case -- probably is on the black market side -- but the people here in WA who are growing for the state are mostly established growers of other crops and certainly not "nasty people".
Illegal trade in alcohol and cigarettes continues even though they are legalized and regulated.