Sometimes it doesn't though. Sometimes the engine seizes because a piece of tubing broke and you left your coolant down the road two turns ago. Or you steer off a cliff because there was coolant on the road for some reason. Or the meat sack in front of the wheel just didn't get enough sleep and your response time is degraded and you just can't quite get the thing to feel how you usually do. Ultimately the failure rate is low enough to trust your life on it, but that's just a matter of degree.