Why aren't there competing methods of marking time?

I asked this question (or something similar) long long long ago when I first came to this board, but was still vaguely dissatisfied with the answers I got, not sure if my main question was addressed. So here it is again:

There are dozens of calendars and means of marking the passing of months/years all over the world, many of them still used today: the Julian and Gregorian calendars, the Chinese system, etc.

So why is there just one worldwide method of telling time? I don’t ever remember of learning of any other systems, not even in antiquity. Why isn’t Ethiopia still using a method where they mark time in basic units that are five of our seconds each and where their day is 23 of our hours long? How the heck did the world get every single country on the planet to agree that there were 60 seconds in a minute (or even how long a “second” is)?

The larger scales of time - day, fortnight, year etc. were instinctive to most folks around the world.

The smaller units of time - hours, minutes and seconds, were differently measured in China, India and other parts of the world before the invention of the clock.

Unlike, mass (or weight) and length (two common “fundamental” units) that could be measured by rudimentary means like a balance or feet or the like, time could only be measured reliably by a clock. So whoever made the first mechanical clock got to decide the units for the future generations.

In some cultures (e.g. Arabia) the length of a month and of a year are not exactly the same as European time. Even the length of a day may vary, being defined as the time from one sunset to the next.

As for minor subdivisions, hours minutes and seconds existed in theory before there were chronographs to measure them. When mechanical clocks were able to measure them (by Europeans who were aware of that metric), those are the units that were in the instruction manual as the clocks found their way around the world. So the units followed the clocks that could measure them.

The French used a decimal time system during the revolution. 100 seconds per minute, 100 minutes per hour, 10 hours per day. The soon reverted to the old way. The Chinese used decimal time through most of its history.

Swatch also tried and failed to popularize a decimal Internet Time that divides the day into 1000 .beats.

And the Romans had hours of variable length - sunrise to sunset was divided into twelve hours, meaning that the hour was a slighlty different length each day.

The Wikipedia page for “Hour” may be a good place to start learning. Different cultures developed different systems. Pages for the 24-hour clock and 12-hour clock also has information about how they came about and became widespread.

It seems the main reason the old systems died out is because they had unequal (non-constant) hours, e.g. based on the time of sunrise and sunset. They died out as mechanical clocks became widespread.