Ask any competitive person how much fun they have competing when nothing is on the line (e.g. playing simulated poker or cash poker) and I think you have your answer.
You make a few errors here. First, your example is something most people don't find particularly fulfilling in the first place. Second, they could give away a portion of their wealth and then there would be money on the line. Third, the fact that there isn't money on the line doesn't mean there is nothing on the line.