Fascinating thread! US here. "9 to 5" is, as PP have said, cultural shorthand for working a fulltime "normal hours" job here, but obviously things like shops, restaurants, and movie theaters (not to mention 24-hour places) have to be open different hours, or longer hours, or they wouldn't get any business (as all their potential customers would still be at work). I remember when I was younger there was a lot of rushing around after my parents got off work, to get shopping done by 6pm, as stores would often close then--but now it seems like places are open until 8pm or 9pm most days of the week. Again, just a couple decades ago, it seemed like the outside world was dead before 10am, and driving around town on a school day morning was akin to witnessing the aftermath of some apocalypse. But now many things open at 9am or even earlier.
I think in general people have a much wider variety of hours and schedules now, meaning that businesses have to be open longer hours to "catch" them. I also think that now people often have very long commutes--there are "bedroom communities" where people have their houses, but every day some huge percentage of the residents commute to nearby large cities to work and even shop. (City-data.com has info about the percentage of commuters in different cities now.) Finding that your new job has a commute of less than an hour (like ONLY 45min) is often worthy of celebration--and longer than an hour is okay, too, if it's public transportation so you can "get stuff done" while riding to work. And then some people have to get up at special times in order to catch the bus, because some routes only hit certain places every 30min or something like that.
I don't know if this is true in other countries, but my understanding is that the school schedule in the US is historically very dependent on the agricultural industry, which was/is huge across large swaths of the country. It's the reason children in the US did not historically go to school in the summer, because that's the busiest time on a farm and children were needed to help out there. Farmers and other outside laborers often start the day as soon as it's light out, so that could account for the early start school seems to have sometimes; and school ending in early to mid afternoon, when there's still a few hours of light, would allow the kids time to help with afterschool chores on the farm. Historically, I believe kids went to school fewer hours during the winter, so they weren't heading off/coming home in the dark; this came in once the school days were standardized across seasons. And in places that had especially harsh winters, there would often be a "winter break" of a month or more in the dead of winter (kind of like a lot of colleges have now between fall and spring semesters) because of the difficult logistics of schooling then--transporting kids in the dark and in bad weather, heating and lighting the schoolhouses, etc..
My point is, I believe the farming schedule drove a lot of the school schedule in the US, and the school schedule drove a lot of other schedules, especially as the parents moved away from farming (where to an extent you set your own hours) and into jobs that required more standardized hours. I also like the idea of businesses trying to overlap with the "head office" on the East Coast--that makes sense to me, too.
camlan was right about the school buses, too. Especially in rural areas, where several small towns feed kids into one school in one town, kids can be on a bus for an hour or more. The big yellow school bus, FYI, is not like a city bus, which will circle the same route all day--if you miss the school bus's single pass by your house/stop, that means Mom or Dad has to take time from their day to drive you directly to school, and they are not happy about that! (Er, IME...) In larger cities, though, I think the city bus routes are often set up to drop students (at least teenagers on up) at their schools, so they probably could catch the next bus and not be late, if it runs often enough.