They do...it's called your rear-view mirrors and turning your freaking head to look.
I'd think they would of come up with a solution for bad grammar by now.
They have cars that have little car symbols on the side mirrors, so when the sensor detects something next to the car (in the blind spot) the little car symbol lights up. It's very helpful.
they have.. you can attach little circle mirrors to your side mirrors, and they catch your blind spot.
Camera in your rear bumper. It's more effective than an additional array of mirrors.
They would HAVE!