Not saying I agree with that argument, or that something better isn't possible, just stating a potential defense to the "tradition" of our 40 hour work week.
Any solution would take a ton of logistics and considerations in terms of wage parity during any transition period, less you want people starving because of bad policy. OR it would take one class of people, those who own the means of production, to create this policy on their own. I see no reason why they would.