If you go back a 100 years, people shat in outhouses and died of TB. Only the rich retired. Why do we decree by fiat that everyone has a moral obligation which

If you go back a 100 years, people shat in outhouses and died of TB. Only the rich retired. Why do we decree by fiat that everyone has a moral obligation which we will enforce via the economic system to spend at least half their waking hours working for most of their lifespan? We don't.