The answer lies in how we can do some bit of introspection. Tell me how lucky do you think you are with your current living conditions? You may not have the best things money could buy or even get the things you wanted but you're living off better than others who have less. It's dissatisfaction and that endless drive of wanting more because people who lived a privileged life will have difficulty understanding how privileged they are so the common route is pursuing what you don't have which is often unattainable. Each person has their own form of happiness conceived and even with having everything, all of what they have could not satisfy anything. Or they just appear to have everything you would likely want but not exactly what they really want for themselves.