First, I don't think smoking fits into the same bin as the other stuff here. If cigarettes were invented today, there is no way they'd be legal. Given the risks they present not only to those who use them, but to the people around them, the FDA would clearly ban them. That they're legal is just a historical accident.

Some food for thought - our own president (a former member of the self-described "Choom Gang") puff-balled marijuana and even gave it a bit of a defense by saying it wasn't any worse than other things. This, at a time when more and more information is coming out about THC levels behind higher than prior decades, and the effects of even occasional use on teens.

And so, we're moving towards a trend of legalization - is this a historical accident as well?