In very large metro areas it , perhaps, would mean little where life goes on 24/7. A common global clock would, however, be just as disconcerting as now to try to figure out what time it is where grandpa lives so as not to awaken him in the middle of the night. Imagine the confusion of an international conference of farmers discussing the time they milk their cows, or fishermen rising early in the morning at 12PM to catch the early worm. Time is, by its nature, confusing. There is no making it simple.
Very good point!
Either way leads to confusion. And....As some have pointed out, in critical areas such as flight there has already been a move to universal time.