Agreed, level 5 autonomy is an ever shrinking number of edge cases. Human drivers also have edge cases like being drunk or otherwise incapacitated by strokes, heart attacks, getting phone calls, old, tired, etc. We still allow them on the road despite this and the notion that those things are some of the root causes of the many deadly accidents each year. Once autonomous cars are obviously safer than that, it will become the norm. We're not that far off from that. First we'll see mass deployment of level 3 & 4 first with safety drivers and when it becomes clear that those are a liability at best, also without. From there to level 5 is a matter of semantics since we'll basically have vehicles driving themselves most of the time.