> because many law abiding citizens who otherwise would have never touched the drug may whimsically decide to try it
They likely wouldn't. Most drugs aren't socially accepted, the gas station wouldn't stock them (and that's usually not what people ask for when they talk about legalization).
Consider LSD. It's illegal, heavily so. But there's 1P-LSD, it's a "research chemical" and very similar to LSD. It has been legal for a few years (and still is in many countries) and has only been made a controlled substance in parts of Europe last year.
If illegality was what kept people away from drugs, you'd expect to have seen a lot of normal people tripping in the last year. But you haven't (okay, maybe you have, it would explain a lot of things, wouldn't it?), and it was really only used as an easily obtainable and legal alternative to LSD by people who want an LSD-like drug because they know LSD.