> Really? What makes 40 hours the magic number?
I think that's the question that TFA, and parent, and a lot of other people in between, are asking.
The answer tends to be 'because that's how it's been for a while'. Or, if you like, it's what mum and dad taught us, and various governments & employers advocate.
Parent was suggesting this is an unnaturally high number, but you're right that coming up with a replacement number - if indeed that's the best approach - is not as straightforward as just picking another one and making forcing everyone else to agree with it.
> How many hours of work is required depends on the job.
...
> How the heck do you know what is required by every single job?
I think this is a dangerous, though obviously prevalent, way of thinking. That every job currently requires ~40 hours a week to perform is, objectively, a ludicrous claim to make.
It suggests a massively tightly coupled relationship between scheduling, specific personnel, and output.
I'd suggest that's a fallacy because western societies have typically settled upon ~38hr of 'being at work' per week ... and apologists try to work backwards from that number on the assumption it's normal / sensible / just right / tenable forever.