ALMS & INDYCAR: Why not race the Indy road course?

As you may well know, the Grand-Am Rolex Sports Car Series is testing this Thursday at Indianapolis Motor Speedway. This poses a simple question that many have asked: why doesn't the IndyCar Series race at the road course at IMS? Indianapolis is the major fan base to the IndyCar Series. While they do have the greatest race in the world and three IndyCar Series races bordering the state, but the speedway doesn't have any open wheel road course racing since F1 left in 2007. My personal opinion is to have the IndyCar Series season finale in Indianapolis at the road course and have the American Le Mans Series and SPEED World Challenge race during the weekend. The reason why I suggest American Le Mans Series racing at Indianapolis rather than Grand-Am is for several concise points. The most major issue is that IndyCar fans generally associate themselves with American Le Mans Series rather than Grand-Am, seeing it as a lesser series with simpler cars and having more association with NASCAR. The next major point is that American Le Mans Series generally draws several IndyCar drivers during the endurance races. My proposition is that they schedule a 8-hour endurance racing the Saturday before the IndyCar race, with drivers like Scott Dixon, Dario Franchitti, and possibly others like Marco Andretti and Tony Kanaan. This race would be a spectacular race weekend and while my cries fall upon deaf ears, fellow IndyCar and sports car fans can agree that a weekend at the Indianpolis road course would be a race for the record books