People think this because in our current social structure, consumption is meant to be the fun part and the release valve that makes up for all the misery, and the labor we do disregards our desires and needs.
People strongly desire processes of self-actualization: feelings of participation in decisions, belonging to group & place, purposeful effort, achievement-by-effort, competence in abilities, confidence in role, recognition of contribution, respect from peers, respect for peers, autonomy, and engagement (losing oneself in the task). I see "work" as focusing on extrinsic motivations such as bribes (e.g. money, trophies, awards, codependency, comfort) and punishments (e.g. detention, prison, assault & battery, eviction, debt). The design of work breaks peoples' psychologically needs, whereas behaviors like consumerism fulfill psychological needs, in a vicarious and unhealthy way. But if the labors of our daily lives fulfilled these needs AND produced the things people needed then we would not have a strong preference for consumption. Time and time again healthy people given the opportunity choose a meaningful life over an infantile life. Even if we are naturally selfish, that doesn't rule out the possibility meeting our needs through productive play.
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