Humans have loss aversion, where instead of considering wins and losses as equivalent, a loss feels more devastating than a corresponding gain.
It is not strictly rational. However, if you extend your body to apply to your psychology, losing a limb can be the end of you, while not getting an extra meal (gain) will merely be a little bit painful.
Daniel Kahneman has pointed this out: typically, our mammalian survival behaviors underlie our materialism and economic decisions.
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