As an Alcohol and Drug counselor, I have had plenty of time to think about this issue and I have seen the horrific effects that addiction can have on individuals, their families, friends, and communities.
First it needs to be recognized that Alcohol is the single most destructive drug for individuals and for society. I do not mean that it is worse than Cannabis or Heroin or Meth, just that it is the most abused drug in our society and that it negatively effects more people than any other single drug.
Second, I do not believe that there is any real rational way to draw distinctions between addictive drugs - as in drug A is worse than drug B and/or Drug C. All such rankings - i.e. hard drugs and soft drugs are mostly superficial. Addiction is addiction - it doesn't matter much what the name of the favored drug is for an individual who is addicted. The progression and the prognosis is the same.
Third, Cannabis is more accepted socially than Nicotine (though not legally). Alcohol is the drug most accepted and honored by society. Heroin and Meth are not accepted - yet opiate based prescriptions and amphetamine based ADHD or ADD medications are accepted - though they are often abused. The point being that as a society we refuse to take an honest look at drugs and addiction.
Fourth, the war on drugs has not worked for generations - I see the grandkids of individuals I worked with when I first started. Has drug use and addiction really been impacted by a drugs legal status? I don't see it.
Fifth, individuals who believe that the legalization of drugs won't lead to increased usage and increased rates of addiction are kidding themselves. Legalization will lead to greater availability and exposure and thus more experimentation, usage, and addiction.
Sixth, legalization would not take the financial motivation/incentive out of drugs dealing - but it would take out most of the violence associated with drug dealing - just like the end of prohibition ended the gang wars over alcohol dealing. You'd just have legal dealers/retailers selling drugs in addition to alcohol.
Seventh, legalization would probably not lead to a major increase in DUI or on the job usage - as those laws would remain enforced and as employers get more and more strict on drug/OH use on the job.
Eight, I don't think there is any simple or good solution. Our society does not do a good job of holding individuals responsible for their behavior and teaching individuals to become adults. We have a lot of 20, 30, 40, and 50-year-old children running around. Legalization of drugs in general would lead at least in the short term to even more problems with addiction - at least for the next 15 to 25 years.
Nine, drug bans, at least to me, seem to be unconstitutional.
Ten, I don't have a nice neat answer for the political decision on legalization or not. Probably the best way to go about it is to push education, then decriminalize drugs gradually and move towards legalization - with a concurrent push as a society towards allowing/requiring individuals to accept personal responsibility for their lives and behavior.
Sadly, regardless of what political decisions are made - legalized or not - I do not fear ever having to worry about being out of a job.