They have driven millions of miles - in perfect driving conditions: great weather, lots of highways, all of it by day (how do I know that? Simple: Google would brag about their AIs being able to drive in rough situations if they were able to do that. But they don't. They just brag about a huge number of miles in undefined conditions...). That is exactly what the original poster criticized. When driving is so easy that it bores human drivers to death, todays' AIs can be better.
The problem is: real-life driving does not only consist of situations that even a child could easily manage. Humans are extremely good at letting their driving skills degrade gracefully when conditions get rough. AIs? They drive perfectly until they reach their limit, then they suddenly pull off epic fails - if no human driver is on standby to resolve the situation immediately.