How about 'the majority of businesses, offices, and people are active from 8-10 or whatever, so when my plane lands at 11:00 am in Tokyo, I can be reasonably confident that I will be able to do standard human business things' versus, what time does Tokyo wake up?

Also every city and even neighborhoods would end up disjointed and on their own system since even just a few miles can make a big difference on when the sun sets and rises.

Timezones were made specifically to link people that were geographically far apart, we had a time before time zones, and people missed their trains all the time because 9pm meant something to pretty much every single person.

I am one of the people with unusual sleep schedules. If you know someone well enough to know their personal timezone then you can use that regardless. It's still useful to know the hours a country usually operates in.