Like I said, dosing becomes difficult because the drug is so potent. Even if you know you only want the smallest hit, it doesn't always work that way in practice (especially if you're not a frequent smoker and aren't familiar with using pipes and vapes, etc).

Plus, a lot of casual smokers think they're supposed to smoke the way they see in movies, or how they did in high school, which is usually not a single, carefully measure toke and then wait 20 minutes.