One possible reason (from the video) might be: because software still has to follow the law. Good driving might imply having to push around the boundaries of th

One possible reason (from the video) might be: because software still has to follow the law. Good driving might imply having to push around the boundaries of the law from time to time, while self-driving machines cannot do that. So they have to hardcode those rules. On the other hand, they should also try to counterbalance human bias as well (protecting only the driver on an accident comes to mind).