I think the idea that we need to work 40 hours is a relic of a time when most work was manual labor. It does make sense if your job involves physical labor. Min

I think the idea that we need to work 40 hours is a relic of a time when most work was manual labor. It does make sense if your job involves physical labor. Mining, working industrial machines, cooking food all requires you to put in those hours and kind of makes sense that your productivity is proportional to how much you work. However, modern white collar jobs don't necessarily need 40 hours. A lot of weekly modern work could be done in less time. In fact, in a lot of jobs, people try to do unproductive work just to fill out the time requirements. Unnecessary meetings, inefficient workflows, paper pushing, make work etc. would all disappear if we just worked less. Another problem with work that requires you to use your brain is that it is literally impossible to stay fully focussed for 8-9 hours every single day. There are going to be unproductive stretches, and you'd rather not work during those than to force yourself into working through them, because those are the stretches when you make mistakes and create more work for yourself, thereby reducing productivity.