I would add to this, that there's probably a lot of lobbying at work as well. In my country at least, the lobby groups for that "other recreational drug", alcoh

I would add to this, that there's probably a lot of lobbying at work as well. In my country at least, the lobby groups for that "other recreational drug", alcohol, and the pharmaceutical industry are both very powerful. There are vested interests in not seeing (a) popular recreational use and (b) promising medical applications take hold, precisely because it's something that can just be grown and is difficult to control and profiteer upon. I'll be accused by many people of spouting conspiracy theories but it doesn't require any mental backflips at all to render it plausible so I'm claiming Ogham's.