Most of these substances you are describing are older; from what I see, I'm afraid the narcotic regulation of more "traditional" narcotics largely rested on societal structure. Tobacco and alcohol are narcotics traditionally used for a long time by Europeans. Alcohol prohibition was tried, but failed in part, I feel, because many of the people in power didn't really, deep down, believe in it at all. (If I recall, at least two Prohibition-era American presidents, Warren Harding and Woodrow Wilson, had private liquor stashes available during their time in the White House.)

Marijuana, cocaine, and opium are not traditional European narcotics. As such, it was something "other people" used; the ill effects were much more easily demonized. There was some fairly racist propaganda surrounding the original Harrison Narcotics Tax Act that kind of demonstrated this point.

Obviously the ill effects of narcotics (such as addiction) are the driving force behind these prohibitions, but in my opinion a fair bit of the current "scheduled hierarchy" of narcotics is not really based on medical science.

Sounds to me like we're in agreement. I'm not sure why you started your comment with "Mmm, no." The laws aren't perfectly consistent on which side of the line they place different substances on (for a variety of historical reasons), but the underlying reason as to why drugs are illegal in the first place is (quite obviously) because of their addictive nature.