I too enjoyed that footnote each time I read whichever discworld book it was.
I was not joking though.
what is 1/3 of 3/4? 1/4?
what is half of 3/4? 3/8.
Again, the other responses show that the point was missed, and in my opinion, it's a big reason imperial feels easy for woodworking.
It uses fractions.
I am all for mental arithmetic, working without measuring etc. However, if you have a pizza and 4 people, you cut across and then across again.
If there's 6, you cut across, then each half into 3. if 8 people.... etc....
Where I think it's actually slower with adding, and I've seen some youtubers adding various measurements, thicknesses, then leaving a 1/64 gap here, and 1/16 there, and end up with 29" 17/64 or something....
However, often fractions are incredibly quick and easy to use, and they seem to disappear in metric woodworking (and many other disciplines using metric).
You could/can have fractions in metric, they're just not used, so my point was not about imp vs metric per se (of course metric is the standard and makes more sense), but that we lost some of the working with fractions, for some reason...