You can anticipate 99.9% of what happens trivially. How often do you get shot at in the car? When people lead with stupidity like that, it's hard to consider their point.
You don't understand statistics. It's not one specific unanticipated event that is the problem, it's that there are millions of them, all the time. You cannot focus one one particular one and scoff at that one, because that does nothing to any of the other millions of unanticipated events that occur. Just on my short drive to work today, I must have encountered at least a dozen unanticipated events.
- Pollen blocked a small part of my backing camera.
- A neighbor had blown a big pile of leaves onto the street. I had to drive around it.
- It started drizzling lightly. Too lightly for my car's auto-rain sensor to kick in.
- A police car without sirens, just blinking lights came in the opposite direction.
- A crow was pecking on roadkill.
- Children were "dancing" around on the sidewalk on their way to school. It's a 50 zone, but prudence told me 20 was plenty when driving past them.
- On an unmarked section of road, another driver didn't know the yield-to-right rule, and almost t-boned a car coming out on the road, swerving into the lane in front of me while (rather incorrectly) tooting his horn.
- Pollen and leaves covered exit lanes, lane markers and double yellow lines. Sometimes severely so. ... and probably lots of other things that I don't remember, because to me, the decisions are ones I just make without remembering them. Focusing on any one of these things is not useful, because there are so many of them. Every day. Every drive.
That any one of them is very low likelihood is irrelevant - it's the sheer number of very low likelihood events that occur that makes it a certainty that unexpected events will happen. And expert systems cannot deal with unexpected events the way humans can. Or, for that matter, even detecting that there is something unusual. Even a small detection failure rate multiplied with the number of possibilities makes for a staggering high number.