I think the car was so smart that it realized the driver was an idiot for getting behind the wheel so tired and falling asleep that it taught him a lesson and purposefully did not turn the bags on.

On a more realistic note, even in new cars like these airbags are optional features depending on where in the world you are, it cuts costs down and is not regulated by governments, hence less safety features.

Back to my earlier point, dont be fools, if your tired, don't drive. It's just as bad as drunk driving.