There are periods when you can make an extra effort, e.g. during a post-secondary education so that you have skills to live on for years to come or before a big deadline that can provide an enormous amount of resources for some time to come.
The examples can be countless. But the fact remains that most people cannot perform at these extraordinary maximum levels for an extended period of time. A few can do it. But today's working life requires that many people make such an effort all their lives. This leads to costly sick leave and unemployment caused by one working inhumanly hard instead of three or more jobs being created. If you remove the possibility of sick leave and social security, this work ethic leads to unrest, crime and perhaps revolution when people become desperate.
Especially in intellectual jobs, the brain has very few resources for this in the form of energy, while these tasks are very energy-consuming. So it is important to save on intellectual work efforts. (Read Your brain at work by David Rock) But manual workers also get tired from too much effort and can then make misjudgments caused by fatigue and stress which can lead to accidents at work which can lead to long sick leave and compensation for the employer.
Then there is the issue of social ethics. Are the employees for the employers or are the employers for the employees?