One will only listen to sports that they truly understand and "like". There is a lot more to auto racing than just making left turns all day but you probably wouldn't understand that aspect. The radio announcers are people who understand the intricacies of the sport. They are able to relay information about setups, pit strategy, fuel windows and statistics. Listening to NASCAR on the radio can be very exciting because you can picture the action in your mind and if you are an avid fan, that can mean picturing details right down to stickers on the sides of the cars.
This rings true with ANY sport. The more knowledge you have of and the more you like a sport, the more enjoyable it will be listening on the radio. This includes hockey, golf and EVEN baseball.
Now for the OP. I'm not surprised that Sirius made a bid an won the NASCAR broadcasting rights. They put their toe in the water a few years ago when they took over sponsoring rights at Watkins Glen. We now have Sirius at the Glen instead of Bud at the Glen. It was then they realized that NASCAR would be a lucrative market and along with Stern would provide a great 1-2 punch.
Adam aka Big Dude