Just curious, when was the last time a race track ran a weekly racing program on dirt?
Angell Park?
Beaver Dam?
UMARA runs a weekly pavement program. NAMARS and USAC had/have one at the Speedrome. How were the car counts for that? How was the grandstand crowd?
Maybe the real question is why doesn't more race tracks run midgets on a weekly basis?

I think you will find race promoters run the divisions they can make money on.