Probably because people’s beds tend to be inside… Plus darkness can mean morning or evening or middle of the night or something else (imagine the person notices it’s dark, looks at the clock and it shows 1pm. We know something’s off because we all experience 1pm as early afternoon).
too bad windows don't exist, it's also not like movies ever fudge lighting to make it look better.
Having a common understanding of what certain numbers on a clock mean and have that be universal can help convey quite a bit of information. 11am means “late morning” in a specific way that you could probably spend a paragraph describing.
or you could just say "late morning" after taking a page out of your book.
Sure, without timezones I’d know what their clock says in London without having to use Google, but I’d still have to Google what time of day it is there and apply an offset to understand exactly what part of the day it is (which is what timezones do already). It’s no easier, plus we lose the ability to culturally share the same reference points.
here's the thing though, you wouldn't need to do that second part. You only need to know what the relative time for london is in the event that you fly over there, or something, and even then. It's still going to be real time, you would just naturally transition over to it. You have no reason to know what time some place else is referenced to, unless you're over there, except for the rare instance where it's convenient.