Underground criminal networks tend not to attract honest and upstanding kind of folk, y'know? Or encourage such tendencies.
No, but old-school stoners with lofty ideals think they can get in and change the system from within, all they've got to do is play by the rules ..... And there are still a few people like that, dealing some of the best homegrown to a select circle of non-arseholes, if you know who to ask.
Anyway, it's not hard to imagine someone joining a criminal gang, getting out of their depth, and ending up going native -- whether reluctantly because their crop failed as is the wont of natural products sometimes but they have to meet a target so much a month for the syndicate so now they're selling short deals but only just until they can get another grow together and then they'll settle up and retire from the game altogether except maybe just raise one crop of percy personal a year for me and my brother cos the missus don't even smoke it anymore, or enthusiastically because they suddenly see how nice guys get nowhere and bad guys get it all.
If you treat people like criminals, they act like criminals. The Rule of Law wasn't enough to keep these people from dealing drugs; what else wasn't it enough to keep them from doing? And in an environment where the more criminally-inclined you are, the more successful you are, anybody with honest intentions is likely to get chewed up and spat out.
This is why I think prohibition is a bad thing. I know I've said this before but if they banned chips, there would still be chip shops -- just not so obvious, and with criminals running them. And besides the odd p!$$ed-off punter with no right of redress there would be fires, electrocutions and carbon monoxide poisonings from ill-maintained frying ranges, poisonings from dodgy vinegar substitutes and fly-tipped cooking fat all over the countryside. All exactly the stuff that regulation and taxation of businesses is designed specifically to prevent.