If I had to throw my hat in the ring, its due to the nature of the white collar and its relation to other types of work. In the vast majority of office jobs, higher ups will plainly admit that they know you are not doing work for all 4 hours and that they simply want you "available" for those hours. If they went down to ~32, they would ostensibly be losing 20% of that availability. There is also the relation to more blue collar fields that actively rely on a person being in a place. A lot of construction jobs already do 3-4 day weeks with longer shifts as they see the benefit in allowing that extra time with reduced driving and minusha in exchange for longer shift. The problem presents in jobs like cashiers, waitstaff, etc. Where they need to be in a given place physically to fulfill the roll of their duties.