It's because jobs are not about work. Nobody really wants or needs 99.999...% of the the things companies make or do. But everybody needs a job. So we have a ponzi scheme - driven by people who can't really do anything. They have a job with a fancy-sounding title. To make it look like they are doing something, they get a bunch of other people who also can't really do anything to have meetings with. Now they are doing something! Those people do the same - so there needs to be even more people, to have more meetings.
It goes like this all the way down until there actually has to be something tangible. It doesn't have to be good, or useful - just tangible. They give those jobs to some programmers. They are smug and think they are actually doing work, but really a programmer's sole responsibility is to give their managers something to have meetings about.
If we admitted things would work better with less worker time, it would start to undermine the whole system, and everything would fall apart. So 5 days (with as much overtime as possible) it is.