The work attire for technical professionals shifted from suits and ties to jeans and t-shirts because the power shifted from Wall Streeters to Silicon Valley hippies as the value added to the economy by computers grew.
This smells like another work-cultural element that could shift easily if several startup-types declare four-day work weeks and find themselves enough runway money to get to revenue-positive.
Maybe it's impossible. But if the folks who champion productivity-through-focus are to be believed, those firms should be X times more productive than five-day firms or crunching firms, the numbers will show it, and the industry will follow.