Revolutionary France had decimal time for a while, but it was not popular. People liked 24 hour days and 3600 second hours
The days in a year are the actual time it takes to orbit the Sun, but that hasn't stopped people. For financial purposes there's the ISO 8601 calendar where years have 52 or 53 weeks. There are the symmetry calendars which have even quarter years and same size months (for example, each quarter is made of a 4 week month, a five week month, another four week month) with every 6 or 5 years having a leap week
But there are so many clocks that would be obsoleted by a change to time.
The most convincing argument for imperial linear measure is the good size of the inch and foot, but millimetres are fine, so the loss of those friendly sizes doesn't hurt
The hour is a comfortable size, a metric day would have a ten or hundred hour day, hours wouldn't be anything like the eight for work, eight for sleep, and eight for shitposting
Working in seconds isn't a good workaround
We would definitely be fucked over in any recalculation of how many metric hours we should spend working
The past changes to week lengths were particularly disliked by the religious people who believe the weeks have been running Monday to Sunday (or Sunday to Saturday) from the beginning of time
And again we have a status quo of two sevenths of a week being for recreation, if we had a ten day week three day weekends would be longer than our current, but would have seven continuous work days
I didn't presuppose the notion of adding additional days to the week. I merely supposed that the leftover days, that do not make a standard 7-day week on their own, should be concentrated to either the beginning or end of the year...
Also January 1 is always Monday, and you could paint the calendar on your wall because every year would have the same dates on the same days, just with an extra week added to December every several years
The biggest problem is that it doesn't track the actual solar day, so farmers would need to use the current calendar to work out when to plant