What I always found funny is the drug trade. No, not medicine I mean the illegal drugs. They typically start at grams(metric) go up to ounces (imperial) then pounds(imperial) then back to kilograms(metric).

I don't care which we use(I prefer metric but won't die on that hill) but wish we would all just agree on one. Like hex keys, you need 2 sets one metric one imperial, same with socket sets. Or go to a machinist and ask them to "take a mil off" of some part, do you mean millimeter or millionth of an inch? Same thing with measurement gear, do you measure pressure in bar, psi, inHg, torr and for more fun are you measuring them positively or negatively... Yes that's a thing. I had a sensor to measure humidity, the output was in ppm(parts per million) but the calibration was done in degrees Celsius dew point but our specificion was in ppm. Those measurements are not linearly related. So let's say the sensor came back out of calibration as arrived(typically it would be adjusted and sent back to us within calibration). Now we had to find the closest measurement we had to the limit in ppm, convert that to degrees Celsius dew point, add in the percentage of reading outside of calibration, add in a extra safety factor, convert that back to ppm, compare to specified limit, determine if any product was made outside specifications and then write a report about if it actually mattered...