The reason is that the rich learn from their successes, while the poor, who don’t have many successes, fail to learn from their failures. And the reason for that is that the human brain is wired to learn better from success than from failure. It all has to do with the positive reward system in the brain. Practically speaking, the most obvious example is how animals are trained for circus performances, how dogs are trained to sniff out drugs or corpses, and the like. Positive reinforcement when they do things right promotes learning more effectively and faster than punishing them when they do things wrong. Apparently, the same principle holds for people.
The authors speculate that successes are more informative than failures. When you fail, you typically already know why and there is not much new to learn. Why then do we keep making the same mistakes? I suspect that habit and emotional factors have a lot to do with it. Compulsive gambling and drug abuse are classic examples of repeatedly doing what you already know is wrong. I remember when I tried many times to quit smoking I only succeeded long term when I took up jogging, which is accompanied by the positive reinforcement of endorphins.
I also suspect that a major reason you learn more from success than from failure is the power of the brain’s dopaminergic and endorphin reward systems. Not only does positive reinforcement feel better emotionally than punishment, there is a real possibility that the dopamine release associated with reward has a direct biological influence on memory formation.
Histed, M. H., Pasupathy, A., and Miller, E. K. 2009. Learning substrates in the primate prefrontal cortex and striatum: sustained activity related to successful actions. Neuron. 63 (2): 244-253.