The problem here is that if I'm doing 70mph+ on the motorway and I see a plastic bag flying in my path, the correct course of action isn't to brake hard or panically try to avoid it - but a computer cannot tell a difference between a soft plastic bag and something more rigid. If the only classifier is that "there's an object in my way, I need to stop" then that's also super dangerous. In fact, there are cases where unfortunately the correct course of action is to keep going straight and hit the object - any kind of small animal you shouldn't try to avoid, especially at higher speeds - yes they will wreck your car, but a panicked pull to the left or right can actually kill you. As a human you should do this instinctively - another human = avoid at all cost, small animal = brake hard but keep going straight, plastic bags = don't brake, don't move, keep going straight. How do you teach that to a machine if the machine can't reliably tell what it's looking at?