As a pre-face, I am politically neutral. I'm just floating this as an idea how I see it. Generally the 'Republican' heavy states (examples being Nebraska, Arizona, Idaho) have a smaller population/acre equating to a smaller customer base than most of the 'Democratic' heavy states (California, Pennsylvania, New York). Logically the auto makers would want to target dealerships that have the lowest potential up side.
Maybe I'm right, maybe you're right, I don't know. Just having a thought.