It doesn't matter how much research there is in support of a 4-day work week.
I work in appliance repair. I do seven work orders a day on average. Each work order that I close makes me a flat rate between 45 and $100 depending on the kind of work that I do.
I cannot survive on 4 days a week. That's 24 work orders that won't even cover my car.
The vast majority of people living in this country don't work in an office. As a matter of fact, last time I checked, I think it was under 15% of the employment force in America works in an office in front of a computer. The rest of us are out there doing something else.
A 4-day work week is absolutely unrealistic.