Take drill bits, for example. Obviously it's much easier to figure out that 11/32" is less than 3/8". Or is it more? No, I'm pretty sure I was right the first time. The metric ones with their 5.5mm, 6mm, 6.5mm sequencing are just too complicated to work with, in comparison. And half a millimeter isn't very precise - it's much bigger than 1/64". Well, a bit bigger. Let's not get into tenths of millimeters.
And at larger scales, of course, base 12 is much easier when it comes to dividing distances. Taking a distance of 2'7" and dividing it by three in your head is much easier than dividing 79cm by three, because... well, 2' divided by three is 8", obviously. If you need to be sure, just tap it into a calculator. That supports base 12...
Anyway, you'll quickly determine that it's 10 1/3", which is much more precise than 26.3333cm. Now I just need to subtract the radii of these two 5/16" holes from that, which is easy - imagine trying to subtract 8mm from 26.3333cm! What folly.