In Germany that is required by law (if your employer sees you working when ill, working too long, working too much - they have to force you to stop). If not by

In Germany that is required by law (if your employer sees you working when ill, working too long, working too much - they have to force you to stop). If not by law, then because almost noone is happy working 60-70h and it puts pressure on others who feel like they also need to work similar hours. Additionally the efficiency gets worse as the weekly hours increase.