Which is where having one central clock would make sense. But it would have to be something based on like a standard physical quantity instead of morning/noon. I’m thinking like rotational speed of the planet.
But now imagine I said "I woke up at 16:00 Z." That's meaningless without the context of what timezone I'm in. That could be early, it could be late, it could be waking up from a nap in the late afternoon.
If you force people onto centralized time, then they'll still start using arbitrary (and worse) measures of relative time, like they'll say stuff like "I woke up two hours after sunrise".
You need additional information than the timezone they live in to call your neighbor on the phone much less someone living in a country halfway around the world.
Oh, 3 hours has passed? That means Earth has rotated X degrees.