I disagree. It would be like having a copilot that stays awake with a driver to make sure the driver is okay. Say that once every ten minutes, you nod off for a half second. The probability of the car's autopilot failing at that same exact time is far less than the probability that half second of lost awareness could cause an accident if there was no autopilot.

No one is advocating actually sleeping at the wheel, I thought my OP was clear about that.