Time zones mean that huge numbers of people have reasonably synchronized schedules. Here in western Ohio, we start work about the same time as they do in New York. If we all used UTC, we'd never know whether there was a decent chance someone we were dealing with a few hundred miles east would still be at the office at 21:00 UTC.

Time zones are great. (By the way, my region was in the Central time zone until sometime in the forties or fifties. It moved east because people wanted to be more connected with the action in New York.)