Probably more because they don't feel it should be illegal, rather than how awesome it is.
Okay, so why should it not be illegal?
Because alcohol and cigarettes are legal so it makes just as much sense for marijuana to be illegal. Marijuana, by the way, hasn't been directly attributed to any deaths whatsoever. Alcohol and tobacco kill thousands of people ever year both directly and indirectly. Alcohol also ruins lives, tears apart families and ends careers. Yet it's perfectly legal.
Imagine there's a planet out there and there's a substance on it we'll call Spice, or Ketracel White or whatever, possession, sale and use of this drug is illegal on the planet but some in the planet's non-ruling population enjoy using the substance and found a means to produce, distribute and use the substance while avoiding the law. In fact people regularly seek out these scofflaws, shady businesses and criminal organizations have been built around this product and it gets the criminals tons of quataloos (the local currency) of nontaxable and untraceable income.
Oh, wait, we don't have to imagine such a crazy scenario because it happened here, in America, in the 1920s under prohibition of alcohol. Look what we got as a result (a shit load of great movies and a great TV series, I guess.)
So why is MJ any different? Alcohol also stands as the "biggest" "gateway" drug, not MJ.
I am not a user of MJ, have never smoked it and never will smoke it even if it should be legalized but I'm clear-headed enough to see that it being illegal makes no damn sense in the same universe were alcohol is perfectly legal when being even completely fair both substances are just as "bad' for the person, their loved ones, and society.
I can understand the laws and restrictions on "harder" drugs like heroin, opiates, etc. But marijuana? Come on! Just legalize it, tax the shit out of it, and then solve some problems!