We have had clocks with the accuracy to display fractions of a second for about 120 years (pre-WW1 stop watches were accurate to the 1/10 of a second) and milliseconds for about 50 years but there is no real use as the second is the shortest practical amount of time the vast majority of humans need in their daily lives.
Becasue there was no one inventor of the clock.
12 hours of daylight existed (ancient Sumer) about 4,000 years before the modern clock (medieval Europe)
Even when clocks were invented, it was hundreds of years before they also showed minutes, and another hundred or so years before they showed seconds.
Soon we will have milliseconds
We have had clocks with the accuracy to display fractions of a second for about 120 years (pre-WW1 stop watches were accurate to the 1/10 of a second) and milliseconds for about 50 years but there is no real use as the second is the shortest practical amount of time the vast majority of humans need in their daily lives.