We are socially competitive animals, just as you can observe in other evolutionarily programmed creatures. We compare ourselves to others, we want to impress mates, etc.
All of which can be achieved in a communist system, only instead of “look at my huge paycheck”, it’d be “look at all these skills I’ve acquired thanks to free public education and more free time”. People would stop mindlessly showing off innane manufactured waste and start actually acquire useful knowledge.