Yea it is strange the consistent proliferation of SAE units globally for certain things like tooling and tires. Not sure where else it is common, I only know about where it affects me on a daily basis with what I do for work. The tires are crazy because the aspect ratio is based off the mm width and the wheel size in inches so now units are being mixed! And square drives (like the half inch chuck key u used to tighten the chuck on ur metric lathe) could just as well be say 13mm instead of half inch, or 10mm instead of 3/8ths but the world just refuses to move on in certain areas. This is to say all the more how badly we need to standardize units of measure globally in our intertwined global world. Robbins and Lawrence was one of the first contractors for us gov to make guns that could be easily repaired with replacement parts in the field (before then all guns were hand filed and built so each part was bespoke, and repairs required craftsmen). When an industry starts with a certain standard (tools, tires, machining) that sets and industry standard which takes precedent over all other standards in that field. This is why all these things have stuck with SAE for so long, but these standards were set 100+ years ago. There is no reason not to move on at this point honestly.