[TrololoTroll]

>however, we did try prohibition. It didn't go well

... Because it was already there. The hypothetical would imply a world where people weren't already high functioning addicts

[IAmBroom]

It also has to assume the average, or even uneducated, person couldn't whip up a reasonably good batch of the stuff over a week's time on their own, given ordinary supplies and equipment found in their own home already. But that isn't true of this particular drug.