Oddly though, I disagree with the summary points, although they're almost impossible to prove.
For example, I think the large majority of Americans can tell you a decent amount about marijuana. Maybe not purchasing info, but general effects, and good guesses on how much folks smoke. I would also guess that if its being legalized in places, than it can't be much more excessive than they're comfortable with. I do agree that they probably can't tell you much more. LSD, Ecstasy, Heroin, Cocaine - they're probably all mysteries to the vast majority of folks.
I would also guess that the vast majority of drug use still happens on a sofa. Obviously, there are people like you say, who use drugs while they're driving or out on the job. Heck, I'm sure a lot of the fast food industry is constantly out of it (see American Beauty). But drugs are still a disorienting state change for many folks, which means a lot of them want to be in a comfortable, safe place when they use them - namely at home on a sofa.