You can stop complaining about any of that and do as you please right now if you are fine with ignoring the society around you. But if you have to function in your local area, work for a local company and so on, the society does generally follow a certain rhythm. And that's the same world over. So it makes it really easy to know that usually business hours are somewhere between morning and evening as defined typically by daylight and if you know the clock is 13:00 somewhere it's daytime and very likely it's business hours and very likely the person is awake.

The time zones just make interacting the world over much easier.