It would kind of be great if they did though, it's not necessarily the same for everyone in the same geographic location.
Now in a world without time zones.
It's now 21:00 where I am (AM/PM doesn't make much sense anymore). What time is it there? It's 21:00. It's 21:00 everywhere on Earth. Does 21:00 mean really late on the East coast? Not sure. Time zones help us answer "What time is it?" or maybe better put "What time does it feel like right now?" with answers of (usually) "morning, the sun is about to rise or has risen recently", "midday, the sun is at it's highest point", "evening, the sun is about to set or has set", "night, the sun has set or hasn't risen yet". Time zones make it easier to know "Where is the sun right now?" in any area of the world.
Yeah, with one global standard time we can always just refer to a day night map (https://www.timeanddate.com/worldclock/sunearth.html) to figure out if it's too late to call someone or schedule a meeting but I feel like it's easier with our current time zone system. I can easily remember if it's too late to call someone somewhere if I remember what their time zone offset is compared to me. East coast is +3 hours, so it's 12 AM there, too late to call. London is +8 hours, so it's 5 AM there, too early to call. Bangkok is +14, so it's 11 AM there, I can call!
As I originally said, though, mine is an unpopular opinion.
That's pretty much what UTC does. The aviation industry does everything in UTC for example, and you convert to local time as required.
> one system that is centered on solar noon at one's longitude and is updated daily at solar midnight
We have that already, it's called (local) Mean Solar Time.