[flowerplough]

could have killed some innocent person while driving

As I also could have, many times. I work rotating shifts in a factory 40 miles away. I haven't killed anyone yet, but several of my coworkers have done so on the morning-after-night-shift commute. The luckier ones have merely totalled their cars and hurt themselves. Gonna test and arrest us all for driving under the influence of working too hard at unnatural hours and living too far from work? No? If not, please do take care to stay out of my immediate forward proximity when I'm meandering home after a long one.

[Tublecane]

“Gonna test and arrest us all for driving under the influence of working too hard at unnatural hours and living too far from work?”

What’s your point? They don’t “test” for sleepiness (although they do pull-over cars for driving erratically, which could be due to sleep) because there is no test for sleepiness. On the contrary, there is a test for drunkenness. You can argue against testing people for drunkenness, but the sleepiness analogy is not appropriate.