It would save me some trouble at work for sure. We have to match timezones and calculate utc from local timestamps for millions of transactions a day from across the country. If local time and timezone was just utc, that saves me the extra steps.
Though days suddenly get really messed up. It would be “tomorrow” in the east coast before it is even dark in the summer. And, worse, it would be “tomorrow” in Hawaii a bit after lunch. In a practical sense that just seems confusing and annoying, so maybe it’s not the most practical outside of datetime data.
We wouldn’t be the only ones. Several countries, territories and islands have half hour offsets from their neighbors. A few even have ±15 minute offsets.