Decimilazation

 Decimalization of money, weights and measures, has reformed old practices, but time has not been decimalized, except for decades and centuries.

Yes—and time is the conspicuous exception. We have decimalized almost everything around it, but retained a rather ancient set of nested ratios:

60 seconds = 1 minute; 60 minutes = 1 hour; 24 hours = 1 day; 7 days = 1 week; roughly 4 weeks = 1 month; 12 months = 1 year.

There is a good historical reason for the first part: the Babylonians' sexagesimal mathematics left us the 60-based divisions of the hour and circle. The 24-hour day and seven-day week have still older cultural histories. But unlike pounds, ounces, feet, inches, shillings, etc., time proved remarkably resistant to reform.

And there is an interesting distinction: time has been decimalized for measurement without being decimalized for ordinary life. We routinely use decimal fractions of a second, milliseconds, nanoseconds, and decimal years in scientific work. But nobody normally says, "I'll meet you at 14.75 hours."

There actually was a serious attempt to decimalize time during the French Revolution. The French Republican calendar introduced a decimal day divided into 10 hours, each of 100 minutes, each of 100 seconds. Thus noon would have been 5:00:00 rather than 12:00:00. It was ingenious, but people simply didn't take to it, and it was abandoned.
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What's especially amusing is that decimalization of time would actually be far more consequential than decimalization of weights and money, because our entire civilization is synchronized to the inherited divisions. Changing the inch to 2.54 cm is merely inconvenient; changing the hour would make every timetable, clock, computer interface, astronomical convention, historical document, and human habit rather unhappy.

And the seven-day week is an even more stubborn survivor. As you were saying earlier, it has become effectively universal despite having no obvious mathematical virtue whatsoever. Seven is almost defiantly non-decimal.

I think it is possible it persits because seven days just seems to fit economically and psychologically.

Yes, I think that's quite plausible. The seven-day week may have survived not merely because it was ancient and culturally entrenched, but because it happens to be a rather good human-sized unit.

A day is too short to organize much beyond daily life; a fortnight is long enough that the rhythm becomes less immediate. Seven days sits nicely in between. It gives a person six days in which to work, socialize, travel, accomplish things, etc., and then a reasonably frequent opportunity for rest or a change of routine.

Economically, it also divides the year reasonably well. A year contains about 52 weeks, so the calendar gives businesses and people a convenient recurring accounting rhythm without requiring weeks to align with months.

And psychologically, seven has an interesting property: you can readily keep a week's sequence in your head. "Last Tuesday," "this Friday," "next Sunday" are immediately intelligible. A ten-day cycle might be perfectly workable, but it would feel rather less natural because the interval between recurring events would be noticeably longer.

There may even be a selection effect here. Once a society has adopted a particular rhythm, economic and social institutions become organized around it, which makes the rhythm useful because everyone else uses it. But that doesn't explain its original persistence; for that, your "fit" explanation is quite attractive.

In fact, I suspect the week is one of those cases where an apparently arbitrary convention acquired genuine utility through long use. Seven isn't mathematically convenient—but perhaps it is humanly convenient.