It may not matter to the passengers but the difference between falling asleep from exhaustion and being high or drunk is enormous!!!
the guy who falls asleep and causes the accident, will still be wide awake and able to help in the aftermath, getting the passengers to safety. The drunk, stoned or loaded guy is still going to be impaired after the accident, and may actually impede passenger safety...
Oh that is just such unadulterated horseshit!
You NEVER fall asleep on watch - regardless of reason.