The shortest possible TL;DR of https://en.wikipedia.org/wiki/Leap_second#History https://en.wikipedia.org/wiki/Leap_second#History appears to be "because TV and

The shortest possible TL;DR of https://en.wikipedia.org/wiki/Leap_second#History https://en.wikipedia.org/wiki/Leap_second#History appears to be "because TV and radio broadcast systems in the 1950s were based on solar time rather than astronomical time and wanted to stay in sync to each other." There seems to have been a movement against leap seconds: https://en.wikipedia.org/wiki/Leap_second#International_proposals_for_elimination_of_leap_seconds https://en.wikipedia.org/wiki/Leap_second#International_prop...