Another aspect of this is that 95% of humanity vie for status. I have have often wondered if this ties in with the fact that 95% of mammals are followers and only 5% have the brain chemistry of leaders. In his video on status anxiety, Alain de Botton mentions that a psychologist in the UK told him that 95% of people in the UK wake up in the morning wondering about their position on the pecking order.

That said, the reason why people like Gates, Bezos, Sim, Dell, and the few thousand others keep trying to make more money is that they fear losing their status. To lose status is to lose admiration and respect. That's why so many people wear brands, want bigger and better houses and cars, etc.

It's caused by a myth that is passed down through the generations - only people that are better are worthy of respect and admiration. And everybody, it seems, wants respect and admiration.