Having said that, I will say that at least tobacco produces a smoke that has a smell and taste that some people find pleasurable. Whiskey, beer, wine, coffee and tea, while they contain drugs; alcohol and caffeine, the drug isn't the main attraction. They are potables with complex flavors. OK, I'll admit the alcohol in whiskey and wine is more pleasurable and of course more noticeable in its effect than the caffeine in coffee and tea but still.
Heroin and cocaine or drugs. They are not ingredients in a potable substance created as a byproduct of its manufacture (fermentation) or in the case of tobacco where nicotine occurs naturally as an ancillary substance like the caffeine in tea. Heroin and cocaine are pharmaceuticals. If legal, what diluted form would they be consumed in? Perhaps one might make the argument that putting the small amount of cocaine back in Coca-Cola might constitute a safe dilute recreational usage tied to a flavor experience. But did Coke ever contain a noticeable amount of cocaine? I doubt it. Otherwise folks would have found it very habit forming.
I don't think the difference in drugs such as caffeine, alcohol, and nicotine, versus drugs such as heroin or cocaine, is one of concentration.
the difference lies in the fact that caffeine, nicotine and alcohol, vodka and grain alcohol like Everclear notwithstanding, exist as an incidental ingredient of the product they are a part of.