That was my thought when considering the difficult and impossible tasks of converting to/from UTC-based timestamps. If we accept that UTC is only for human use then we should also accept that humans can't tell the time of day down to the second just based on their circadian rhythm and the Sun.

Given a TAI-based timestamp a hundred years in the future we can be pretty certain in saying "yeah it will be around lunch time" (assuming there is no major changes in the solar system that would probably have such an impact on the lives of every human that nobody would care about this event anyway).