The top level comment is about using brain-chemistry affecting substances to maladaptively cope for difficulties in life. Some people use substances to work around the root cause rather than addressing it head on, which is generally bad.

With alcohol, you can drink and feel loose instead of dealing with whatever's got you stressed and pushing your boundaries. Maybe you can't keep up at work. You should fix that instead of drinking, but drinking lets you get by well enough, so you're less likely to fix whatever's causing the problem in the first place.

With coffee, you can drink and feel alert instead of dealing which whatever's needing your alertness past your boundaries. Maybe you can't keep up at work. You should fix that instead of drinking, but drinking lets you get by well enough, so you're less likely to fix whatever's causing the problem in the first place.

The point is that, yes, many people use mind-altering substances to cope with life and, yes, it can be a maladaptive coping style. But that includes benign stuff like coffee where people would laugh if you suggested outlawing it. So the criteria of "people use this mind altering substance to avoid dealing with problems in their lives" is a bad criteria alone.

You have to put substances along a spectrum from benign coffee to malignant heroin and figure out where to put each substance and where to draw lines of government control. I hope coffee and potentially alcohol establish that a black and white approach doesn't cut it.