Those drugs are even worse but not enough people abuse them anyway which is why they're not that big of a problem.
Did enough people smoke weed in the past?

Not enough people smoke salvia. If people smoked as much salvia as they did with weed, then it would be an issue. Oh wait, it is, isn't it? There's already an issue with that kid commiting suicide. That's just a start.
It's already all over the news these days. Kids are abusing salvia. Salvia IS becoming an issue.
What is NY doing right now? They're making it illegal.
Soon the whole country might do that.

I believe it wasn't until way later that weed became an issue and too many people started abusing it. Nowadays we smoke weed a whole lot more than we used to.