Barring some radical breakthrough, progress usually follow an asymptote. Waymo has reached their asymptote after perfecting their autonomous driving for over 10 years, and is still not confident enough to launch it even in their spherical-cow geofence.
The real world is full of edge cases - cameras fogging up, proximity sensors confused by ice buildup, thick fog limiting visibility, sun low on the horizon blinding the cameras, badly marked construction sites, black ice, line markers under snow, potholes, slush, contradictory traffic signs, deep puddles, worn out ruts, suicidal wildlife, road debris, etc. etc.
