> You already can get rid of time zones by only using UTC.

UTC has leap seconds. You are thinking of TAI:

* https://en.wikipedia.org/wiki/International_Atomic_Time

I suspect most people on the "abolish time zones" kick don't actually deal with people in other timezones very much. By knowing what timezone someone is in, I know instantly--without even consulting their calendar to find out what their usual working hours are--whether 2pm my time is a reasonable time to propose a meeting.

Similarly, every time I travel to a city in a different timezone, I'm going to have to find out what usual business hours are, when dinner typically is (which admittedly varies a bit from country to country anyway), and so forth.