Wikipedia tells me it was come up with in 1923, long after both global trade and the industrial revolution. You need all the countries to agree on the same calendar system or commerce is really hindered. It was way too late to change in 1923.
The French tried to change the calendar to something more sensible and closer to metric after the French Revolution. It did not last long.
Things seem to work just fine with the calendar we have anyway.
Also, it could be worse. The Mayans had three different calendar systems- a solar calendar, a lunar calendar, and a 260-day calendar which we don't know the origin of, but I like Dr. Ed Barnhart's theory that it's very close to a human gestational period.
It would have worked if the rest of the world (or at least the major European powers) were on board. But since most of them were still ruled by kings, that wasn't going to happen.
And Christianity being a major religion in Europe which teaches a 7 day week, and I believe Islam in the east does the same. China also used the 7 day week at this point, too.
I was responding to you saying humans seem to always divide by 7. It’s an interesting point you make that it’s been done for a long time but we are saying two things.
You actually made me think of something I’m gonna go ask the Hebrew specialist, did 7 days in the Hebrew Bible mean 7. I know 7 is their number for a lot just like 10,000 in Chinese. :)
A week is one quarter of a moon cycle. Basically we either have to choose solar or lunar and solar makes more sense because of seasons. Problem is we chose both.