I think a technical solution for a technical problem is better than a legal solution to a technical problem, especially since the hardware and infrastructure for such a widespread camera system (not to mention the associated state bureaucracy that would be required to operate it and process the fines) would be unavoidably expensive. Even if it were somehow cheap and simple, monitoring every piece of road would be impossible. And then you would need to legally define "tailgating" and correct for edge cases such as when the person in front brakes suddenly, but the camera still sees it as tailgating.
