It’s not “niche” if you do things synchronized to GPS timestamps. (i.e. a significant portion of telecom, a bunch of electrical grid stuff, etc).
Anything using GPS as lock references to synchronize stuff that needs to be aligned to the millisecond absolutely cannot tolerate stuff like “the leap second smear”.
The vast majority of people using date time libraries don’t need to represent dates before 1980 or dates after 2036. It doesn’t mean you just bury your head in the sand and ignore a pretty critical part of how time representation works.
Anything using GPS as lock references to synchronize stuff that needs to be aligned to the millisecond absolutely cannot tolerate stuff like “the leap second smear”.