Personally, I am generally willing to accept most behaviors - as long as - you do not endanger others, but in the US, with our tremendous "sprawl", driving a car is almost a necessity. And in the wrong hands a moving vehicle is certainly a dangerous weapon.
Intoxicants for recreational use should be available to adults, but driving a car while impaired is simply unacceptable.
There's a debate on this, because At What Point is the action endangering, Others.
There are 4 pillars holding up a bridge. They can be operating at 50% capacity each and the bridge would not fall. EXCEPT on the day by chance there were too many trucks.
The extra capacity of each pillar is a Necessary Buffer against unforeseen outcomes, which by rules of limited consciousness will always occur, and is always catastrophic.
Every unenlightened/uncontrolled/unplanned diversion weakens the collective.
This isn't to say rules can never be bent or modified, but the collective capacity is always in play.
One extra person worth of man power or Brain-Power might be the difference between a power plant exploding.
In the case of most Recreational Substances, it is similar to leaving Performance on the table or Squandering it.
There should be a way of medicating <recreation-ally> that produces minimal harm. but such a system would require quite alot of engineering, and it's empirically true that for the majority of humans, Self-Monitoring/Control is inadequate. Proof- Kensington Philadelphia
The alternative is to waste tax dollars and public resources enforcing laws against every personal habit that doesn't "help the collective", which is, IMO, way more harmful than just allowing people to govern their own personal habits.
For me the line gets drawn at physical harm. If you're holding back your family's personal finances due to a drug habit, that's a personal problem. We should offer programs for assistance if you're seeking help getting out of that situation, but the consequences should purely be societal. That is, if you refuse to help yourself and address the issue, you'll suffer natural consequences.
If you get behind the wheel of a car drunk/high and start drive erratically, then you're an immediate threat to people's safety. You don't get to have a license anymore until you've proven that the behavior is corrected. If you do it again anyway, over and over, you're a threat to public safety and may need to be institutionalized until the behavior is corrected.
My view on America's prison system goes way beyond the scope of this thread.