Some years ago, one very smart american coworker told me why the US chose the non-metric system. Back in the days people had to divide things - land, materials, lots of things equally between people. If your system is "12" based, then you can divide by 2, 3, 4 and 6 (well 4 and 6 are obvious), but if it's metric then it's only by 2 and 5.
Not that you can't divide by 2 and 5, but you'll get rational numbers, not integer.
Not sure how true this story is, but even if it's not, it's still amazing :)
(Another story I've heard from him was why cities around Los Angeles were named after saints - San Diego, Santa Monica, etc. - All of them were connected by a day run with a monkey - this way creating a support for the established christian missionary settlements - something like it).