Why would any organization fighting for funding be inclined to undermine their reason for existing? And why would any rational person be interested in what they have to say about a topic that is well outside their area of expertise (medicine)?
> It is difficult to get a man to understand something when his salary depends on his not understanding it.
Ethics. Morality. The desire to not be a horrible excuse for a human being inflicting needless pain and suffering and destroying the lives of the people their agency is ostensibly charged with serving. Not perpetuating the horrible status quo that's corrupted the spirit of their mission and accepting the will of the people.
Weed isn't the drug that your hippy parents smoked in the 60s anymore. Years of selective growing increased psychoactive substances to insane levels never found in the plant previously. It was also the logistical problem created by prohibition that made this process beneficial. Sure, people would have done this anyway for the drug to become more potent, but I believe free availability would have countered this development.
Of course even with its potency it is still one of the softer drug. Alcohol can be just as destructive.