While people do indeed need proper rest and downtime in order to perform to their maximum potential, exactly how much rest they need changes from individual to individual. A "one size fits all" approach through legislation will necessarily mean that some people who could work quite comfortably with no ill effects will be prevented from doing so.  The choice to work or not rightly belongs to them, as does even their decision to risk their health. It might be worth it to someone to take a chance on sleep deprivation in order to earn more pay.