If you look at who owns most of the ovals, it makes sense why they don't run more. I saw IndyCar races at Chicagoland and Kentucky that were as good as any racing I have ever seen. Not a lot of fans were there either. When the IRL first started there were several short trackers that had chances, and no one showed up to watch.
I actually don't mind road racing. I will take that over fenders on a dirt track any day.