Pretty common to talk about measurements of 1/2, 1/4, 1/8, 1/16 of an inch and find those graduated on a ruler. Or 1/2, 1/3, 1/4, 1/8 of a cup for liquid measures, etc.
But then machinists generally work in thousandth or ten-thousandths of an inch.
And most of the kitchen stuff is a chicken-and-egg problem: the US used 1/2 cup because that's what it is used to, the rest of the world has recipes calling for 50g of flour. If the US was used to weight-based measurements everyone would have a kitchen scale with 0.1g precision lying around, instead of a bunch of measuring cups.
These incessant arguments of "why is someone doing something different than what I'm used to so stupid" are funny if not tiring. Why not ask why are there so many different spoken languages in the world instead of just speaking like me? We could go into if Rust is better than Go, or why Romulans are better than Klingons. The problem is that nobody wants to understand the differences and just want to rag on the person opposing their views. Yawn
Why are you conflating speed and precision? A cup-ish measure would be 200g and no one is measuring that to .05% accuracy.
On the flip side, good luck getting .1g precision out of a measuring cup if you need it.
The point you're not willing to accept is that there's no dying need to be that precise and using "cup-ish" measures is good enough and works just fine.
Precision is orthogonal to the unit.
Everything is standardized on IEEE floating point. ;-)
It's a headache to maintain collections of parts and tools such as taps and dies for both standards.
The biggest shift is simply the obsolescence of old stuff, and emergence of new stuff. And industries have adopted the practice of reducing the overall variety of parts needed. I work in the development of industrial measurement equipment, and where a design might once have had 30 different sizes of fasteners, now it's 5, all metric. Designs rarely need nuts and spacers any more. Washers are integrated into the screws. No more "philips" or flat head screws. And so forth.
What is the modern approach where nuts/bolts and spacers would have been used?
> No more "philips" or flat head screws.
Torx? Rivets? Something else?
At where I work, we use hex head (trying not to say Allen). I see lots more Torx in products as well.