No matter how high our collective standard of living is, it just raises the bar for what people feel entitled to without making any effort to earn it.
No matter how much you have, there is going to be somebody that has something that you don't, that you want.
This creates dissatisfaction that either drives you to try to obtain it, or to feel resentment at the differential.
This is true of all humans, and even lower primates.
A monkey will be happy to receive cucumber as a reward until he sees another monkey getting grapes, at which point he will throw his cucumber at the researcher in jealous rage.