There are certainly plenty of "users" of alcohol and tobacco, to provide statistically significant analysis. I would have thought it would be the less commonly used, and/or recently introduced, illegal drugs which would cause a problem of statistically significant analysis.
But, if you don't have actual figures (no, nor do I) then, no point in banding opinions.
For the record, I am of the opinion, legalise them all, put appropriate health warnings on them, regulate quality, and tax them, just like alcohol and tobacco. Plus of course, appropriate laws for criminal behaviour whilst under the influence.
I'm happy to agree to disagree with your first point.
And happy to agree with your outlook on the second.