I don't think that's true. There's an assumption that before you start drinking or taking drugs, there's a decision to do so and at that point it's expected that an adult can make the correct choice knowing the potential outcome. Not the same with a tired worker, does an 8-12 hr. gig, gets in the truck and needs to drive it someplace. No decision to be made about "my actions are going to make me fall asleep". It's not as clear cut as knowing the results of drinking alcohol. As well and as discovered with 2 NYC area commuter rail crashes, sleep apnea can go completely undiagnosed and a result a person is more prone to nod off when they otherwise think they are OK. Can't say if that's the case here.