Perhaps the government know exactly what the power of Cannabis is and that is exactly why they do not want to given to the public unless they have found a way of taxing, corrupting, co-opting it, controlling it, and giving it a heaping dose of government bureaucracy to waste lives and time and suck our energy.
Governments and their minions or Micro-Managers as explained in The Lego Movie are here to suck our energy just like the Matrix. They are giant and persistent energy harvesters. The term blood-suckers is not so appropriate as energy harvesters because energy is the sum of time and our efforts and that is what they want to control and lead astray away from the truth.
Anytime we are asking the Government for permission who can be sure it will take years for the approval to come if you are lucky, otherwise it will be stuck in endless Micro-Management until they have found a way to corrupt the original idea and trouble makers.
By the way The Lego Movie and The Matrix are the same movies or films. See the sources for details. If Weed is now being covered by the Mass Maggot Media then we can be sure something is being planned for the population in terms of deception and deceit and controls.