I've seen studies that indicate that reducing the work week can improve productivity per hour. It can be a net gain, allowing people to be more focused, make fewer mistakes, etc.

Sort of like when you pay people a bit better than average for the industry, thereby fostering improved employee retention and lower turnover. It pays for itself over time and has additional benefits down the line.

This seems like a good idea to me. The 40 hour work week grew out of technology improving productivity such that some people were making good money and then there was higher unemployment to go with that. It was intended to share the wealth, primarily. Now we look back on normal working conditions prior to that and deem them to be inhumane.