Marijuana IS addictive; it's HIGHLY addictive. People don't view it as such because it's fat soluble. Because it's fat soluble, it's half-life is much longer than water-soluble drugs, meaning that it stays in your system MUCH longer, but the flipside of this is that withdrawal symptoms are much less profounc because of the longer half-life.
When I was a substance abuse counselor, I found many folks whose idea of recovery was the "Marijuana Maintenance Program". They were willing to give up all drugs, including alcohol. (I had lots of clients claiming they "didn't like" alcohol, and that seemed evident.) But these folks HAD to have their weed. They HAD to have it, KNOWING that it would stay in their system, KNOWING that they'd test positive for employment drug tests, etc. They HAD to have it, and refused to live without it. This was NOT logical, but it was evident that having weed was a part of these people's addictive norms, and the most stubborn part of it.
I'm not in that field currently, and the world of Medical Marijuana Cards, etc, is a brave new world on this topic. There are thousands of substance abusers, including those who are now looking to "get on the card" as if it were just another psychotropic medication. I don't know what exactly I think about this, but I do know that we have created a society where millions of people are desperate to feel better than they do normally. I also know that we have created a society where millions have been traumatized and suffer from some degree of post-traumatic stress, up to and including PTSD. Cracking down on Big Pharma, Pill Mills, and the like won't do a thing to relieve THAT problem.
