Why even 3... two would probably be sufficient, that's what people are accustomed. Eastern/Central; Mountain/Pacific. Then we are down to 14, even better!
It should be incumbent on the broadcasters to make sure that those in their viewing audience are adequately served. The airwaves are a public trust and broadcasters have been granted the right to use those airwaves. With that right should be a responsibility to ensure that everyone has access to those signals. If a broadcaster is unable or unwilling to provide an adequate signal to a viewer in his defined service area that viewer should be freed to obtain that programming from any provider willing to serve his needs. In other words, not only should waivers be easy to get, broadcasters should be made to pay for a means of alternative distribution (cable, satellite, repeater) if they will not grant one.