Why? Because our preconceived notions of a "day" is that it must mean the sun has risen and set. I get past this pretty easily by imagining I'm in space where I would have to divorce that from my mind.
Or because when someone says “I’ll call you Tuesday afternoon” and your day changes at 1pm (historic time) it’s a little confusing. Or does afternoon now mean 12-5 UTC? So until we adjust everyone’s semantics, no one has any idea what “Tuesday afternoon” means.
I am not in favor of abolishing time zones, but I am sure we will find better ways to communicate with each other about time if that were to happen.
We can’t even agree on whether the earth is flat, or how to spell/pronounce aluminum. Changing thousands of years of traditions because programmers are tired of dealing with the vagaries of time zones isn’t going to be terribly successful.
And that’s really not an argument against the idea. Time zones are a construct that isn’t necessary any more. And it literally wastes people’s time with unnecessary legislation, unnecessary calculations, and unnecessary notions of displaced relativity.
As I originally said, though, mine is an unpopular opinion.