Why do almost racers doing the Amazing Race?
Is it because of desire to interact with other teams or see many places around the world or test their own skills at many different thing, or the publicity for their causes or selves, all things cited by teams as a cover story?
I say "No Way!" They are doing it for a 9% initial opportunity to win $1,000,000. With then prizes for the other places, the net present value of being on a race averages above $100,000 initially for all teams. That is the primary reason they are doing it. Just listen to their pre-race comments.