Originally Posted by imageWIS
That's because BMW doesn't have another car to race.
The M3 is being raced, and there were rumors the M6 was being prepared for a GT car series. Also, the 320si is a homologation for European touring car series many of which they've successfully raced for many years, including a championship last year, and winning overall with a diesel 3 at the 1998 Nurburging 24 hour race --- the first diesel engine to win a 24-hour race. The 3s in both E46 and E90 forms are being raced with factory-backed packages. Minis are also being raced with factory support in the form of manufacturer cup points. Even the X3 was raced, and won the AlCan a couple of years ago. So BMW does have many other cars that can be and are raced.
About the only thing they aren't doing is a GT prototype car (unless you count the Dinan-powered Riley in Rolex), but running an F1 team along with their own open wheel formula series are pretty good substitutes. And we aren't even talking about their motorcycle success, yet.