I’ve written about time zones before here. The short answer is that before travel started to move at the speed of railways, there wasn’t a major need for them — people reckoned time locally, and they weren’t carrying things like watches or other timekeeping devices that needed to be adjusted. The speed of travel was such that you might gain or lose an hour every week or 10 days or so — not noticeable if you’re resetting your local day at noon anyhow.