I have an opinion,
not wholely provable, that when people do a lot of overtime they spend a lower proportion of work time on productive work. Places with 40-hour weeks seem to be more productive than places with 80-hour weeks. People with decent work hours still play around on the job, but do more of their playing during non-work time. I am not talking about exceptional situations which arise occasionally in many kinds of work - but I am talking about permanent exceptionalism.