i suspect one reason we still use 12 hour clocks instead of 24 hour clocks is because the numbers above twelve are too much of a mouthful to use in everyday speech. who wants to say "twenty two o'clock" when you could say "ten o'clock"?
i say this as someone who has set all my devices to use 24 hour time but who usually translates to 12 hour time when talking to people
mostly because it's what people expect. but maybe also the other reason?