We are stating subtly different points here. Holding 32 hours a week constant, you are arguing that 4-day workweeks reduce cost to the employer, and I think you

We are stating subtly different points here. Holding 32 hours a week constant, you are arguing that 4-day workweeks reduce cost to the employer, and I think your arguments are at least situationally true quite often; however, I am stating that shorter workdays would lead to greater average value per hour spent for my employer from me, which I think is also true in my case. The deciding factor is whether the difference in value generation is greater than the possible cost reduction you propose. That is a difficult question to give a definitive answer to, especially because there are large groups of people who want to spend as little mental effort as possible at work, to whom my personal preferences obviously don't apply. TLDR: You bring up an interesting point. Thank you for your reply.