Once upon a time it took a year to travel halfway around the world on a boat and so it made sense that “noon” always meant “sun as high as it can go.” Just for custom. Especially because the bank didn’t open at “9am sharp,” it probably opened at “whenever the banker was done with morning tea and felt like it.”
The concept of Local Noon made even more sense because words couldn’t travel any faster than people so who gave a crow’s fart where the sun was in the sky when they wrote them down. Your BFF back in England wouldn’t see them until, like, next YEAR. You had only one good reason for knowing “when” “noon” “really is” at your location (in comparison to, say, “noon” at the Royal Observatory in Greenwich) — so you could calculate your longitude and know how far around the Earth you were from Greenwich. Whether your BFF was drinking their morning coffee or afternoon lager was totally secondary.
The ISO 8601 timekeeping standard is just epicycles grafted onto that old wooden-sailing-ships orrery.
As I type this, the time RIGHT NOW for EVERYONE on Earth is 2016-03-13-23:42:28.916358. Even in Arizona. Whether it is dark or light, whether the nightly news is on, whether it is Beer O’Clock or Half-past-Coffee is an entirely local affair. My bank will open at 16:00 sharp tomorrow in Zulu time. I’ll call that “9am” but that’s just local convention. Like legal pot and people saying “thank you” to the bus driver.
Do you have any idea how much easier life would be if we were all on Zulu time? How easy it would be to schedule international phone calls? How much server configuration I will never have to do again?