For those who abhor non-decimal factors in units, why do you put up with our current system of time? Short of tweaking Earth's orbit, we can't do much about the number of days in the year, but all the subdivisions of a day are entirely up to us to control. We don't need to follow the Babylonian system of 24, 60, and 60. We could use centidays and millidays for ordinary timekeeping. A centiday is 14.4 of our traditional minutes, and a milliday is 1.44 minutes. Once we made the switch, we'd easily change our habits to make classes, meetings, and TV programs last two to four centidays, cookies bake in one centiday or a bit less, a work day is 33 centidays, etc.
Quick: if an engine rotates at 2000rpm, how many revolutions does it make in an hour? A day? If the same engine rotates at 3000 revs/milliday, you immediately know it completes 30,000 revs/centiday, or 3,000,000 revs/day.
Converting meters/sec into km/hour is not necessarily intuitive to most people, but converting m/microday into km/centiday is just moving the decimal.
So why don't we make the switch?
We'd have to replace all clocks. We'd have to get used to thinking in centidays and millidays. Camera shutter speeds, frequencies on our radio dials, frame rates of movie cameras, the standard pitch of musical instruments, baud rates of serial data transfer, and our AC power grid are a few of the random things we tie to the second. We measure pulse, respiration, and the speed of rotating machinery using the minute. Our system of time zones and the speed limits on our highway are tied to the hour.
There's no doubt in my mind that, after we transitioned to metric time, a lot of math involving times would become much simpler for humans to deal with. I also have no doubt that many of those who grew up with our present system of hours:minutes:seconds would have difficulty adjusting to decimal time. And the retooling that would be required would be horrendous, as would the synchronization of such things as airline schedules and teleconference timings during the transition. I'm confident I will not live to see the adoption of metric time, and I suspect my (as yet unborn) grandchildren won't, either. Because we're unwilling to make the change and suffer the cost ourselves, we're condemning future generations to suffer through the difficulties of the current system until such time as they take it upon themselves to adopt a sensible set of measurements.
If you understand why the world still uses hours:minutes:seconds, you understand why the US is still using pounds and feet. The arguments for the status quo versus decimalization of measurements are the same in both cases, at least qualitatively. The relative magnitudes of the costs may be somewhat different of course.