Replacing all car mirrors with cameras is not a good idea. All it does is add unnecessary cost to a vehicle, and the cameras would actually not be quite as good as a standard mirror.
The existing automobile mirrors do their jobs quite well. They require zero electricity to operate, and they work when the vehicle is completely powered off. Mirrors are also very resistant to normal wear and tear. They don't break down, display erroneous images, and they even work somewhat when they are broken.
On the other hand, cameras and their corresponding screens are far more inferior to a standard mirror. They are much more easily subjected to damage. In a vehicle, the sensitive electronics can fail over time due to stresses such as constant vibrations. Connections can come loose, etc. Using cameras can be somewhat disorienting. The screens would not typically be in a convenient, or logical place. It could be hazardous because the driver would be looking at a screen in the cockpit instead of looking around the car, and get a false sense of security. 538
Anyone that has a backup camera knows that the camera becomes useless if it is at all obstructed. A small speck of dirt is all it takes to effectively block the view. The biggest drawback of cameras is that they do not operate at all when the vehicle is powered off. When a vehicle is parked in a city, typically the driver checks their mirror to make sure it is safe to exit the vehicle. If the vehicle is parked, and turned off, then they would lose the ability to check for traffic and could result in injury or the loss of life.
Cameras are great for certain purposes. The backup camera is very useful because it allows you to see objects which are not visible from standard mirrors. It lets you see how much room is behind you and is very useful when parking, and also attaching trailers. I could see other uses for cameras on vehicles such as on big trucks. Tractor trailers especially, have very large blind spots. The biggest blind spot is on the passenger side which is sometimes called the "no zone". When vehicles pass trucks on the right, usually the driver cannot see where they are. The addition of cameras would help to greatly reduce the number of blind spots, and could result in the reduction of accidents. 538