Earlier quoted context omitted.
40 is probably the most optimal way to extract the most value out of the most people. If only some worked less, there would probably be bigger HR overhead, like you say, plus those individuals would be less communicable. In reality, those companies who extract the most value from their workers are able to outcompete others, so the system stays. If company would pay less to workers (for less time used, half of "normal…
I feel like we should be doing something like requiring paying overtime for over 30 hours a week. The complication here is countries are competing with each other as well as internally. That said, most jobs are local, so cheap construction workers or child care workers overseas don't compete with local ones. This combined with doing something about housing prices seems like it could work.
That's also why building homes is so costly. Transporting non-local materials costs more than making them near. Then you need to support builders, plumbers, electricians...