Fully automated cars can for certain reasons such as imperfect code and thus glitches, be insanely dangerous. The technology is there, and there are some car companies who are working on it actually. In fact, there are no fewer than two states in which fully self-operating vehicles are legal. But it's still a matter of how automated can you make it? The average consumer won't be happy until they sit and tell the car where to go and it can take them where they specify. Even then, you'll have the out crying question of what happens if the AI bugs out somehow and potentially leaves you in manual operation mode without warning?
The reasons these don't exist comes along the lines of, do they even know they exist? Do people who are familiar with the standard version currently in use, recognize this design? And of course the bottom line in all of it, how much would it cost to replace a substantial portion of the lighting systems to create precedent to warrant them becoming a standard? (Think not only the costs of material, installation, disposal of old equipment, but also educating the general public.)