Kart Racing Is the Future
It's obvious what the problem is. The solution is to lower the barriers to entry. Make it more accessible to more people and there will be more participants.
Money is not the only barrier to racing. It's a big factor, but it's not the only one. The other main issues are location and technical knowledge. Racing requires a place to race and, if you own and maintain your own equipment, the know-how to do so.
Most forms of racing make it painful to participate by being an expensive chore. The tracks tend to be far from population centers, the equipment expensive, and the amount of equipment preparation is both time intensive and wasteful. Does it make any sense to have to throw away a set of tires after an hour of use in order to remain competitive? That's not the way it should be.
Kart racing can be quite costly, but if it were properly organized and promoted could serve as a very cost effective testbed for new technology that could be scaled up for larger vehicles (motorcycles, passenger cars, etc). A lot of data could be gleaned from all the cyclic loading and different drivers that karts would be subjected to in a short amount of time. If karts were powered by electricity, batteries and motors would be prime examples of things that could be tested.
Beyond that it is also also ideal for new media formats and social networking. People are moving from passively watching racing on TV to participating in it themselves, and sharing their experiences with others.
I've done a lot of racing in a variety of vehicles and formats and can tell you hands down some of the most fun is racing with good competition in equal equipment. The machinery might not be the most "pure" or sophisticated but that is a secondary concern. The quality of the racing (and the camaraderie) is incredible, and the price is downright cheap compared with any other form of motor racing. It is the future of racing. Here's are two recent clips:
Indoor Kart Racing MeetUp from Volta Grand Prix on Vimeo.