They cause a hassle but are required. The Earth's rotation isn't perfectly constant, so without any adjustment we would keep drifting away from solar time.
Doesn't it convert to within some margin for error? Checking Wikipedia, I see that the delta between TAI and Unix time has only drifted 27 seconds since 1972. That should be more than sufficient for your average mundane human readable purpose.
It's easier to just keep high noon at the Greenwich observatory as the defining datum, since most worldwide coordinates ultimately reference back to it, being 0deg longitude.
Ultimately, either time or location would need to be adjusted, and it's easier to do time. Plus it's consistent with what's been done historically.
https://en.wikipedia.org/wiki/Leap_second#International_prop...
But those dozen IT people think the trade off is really worth it (for them)!
And this kind of thing can never be undone. See: NTSC "60" Hz actually being 59.94 Hz due to the transition between black and white and color TV. Monitors today still have this lasting effect for consistency's sake.