It's pleasurable, and hard to tax when it can be grown anywhere, therefore illegal. How many other substances or plants are judged on medical benefit? :(
In 1968 the rock band Stepoenwolf (spell check won't let me spell it correctly) wrote "Don't step on the grass Sam". It's hard to believe we're still having this discussion nearly 50 years later.
They were right about one thing- it is a gateway drug- a gate for the government to enter your life and ruin it.
I'm not a smoker, and would prefer that my kids never smoke it, but I fear law enforcement involvement more than I fear the substance itself. I think most people feel the same way.