One of the issues that is missed with broadcasts and the written articles (in all sports) is the mental struggle that people go through – the brain bsttle. Even if participants are “miked up” (so you can hear their mumblings) there is a lot of internal drama that makes races the most personal of highs and lows and that element just cannot be conveyed.
The feeling of completing my first marathon (and in a decent time) was so internal the outside observer wouldn't get anything out of that moment. But for me there was pure elation!
Also, a runner pasing another runner is not as dramatic as a race car driver passing another. There is a higher element of danger with the race cars that makes the occurance “more” exciting. This is unfortumnate but to really expand interest in running races people really need that personal experience.