>Why do we work five days a week until we're old and getting ready to die?
Capitalism requires us trade our labor for the compensation necessary to buy food, clothing and shelter until we're old and our labor is no longer worth anything to the market.
Also, because of the Jewish Sabbath, and later because of unions and labor laws, since the norm used to be a seven day workweek[0].
[0]https://en.wikipedia.org/wiki/Workweek_and_weekend#History