I know I’m getting old and repeating myself BUT Metric whilst it may be more common is not the ONLY system in COMMON use, In hydraulics and pipework Imperial is normal world wide, JIS a hydraulic type has a form that looks like an American JIC but uses BSP, aluminium sections are often Imperial, Then there’s structural steel, WHY use sizes like 102, 203, 254, 305 Etc ? In fact most european languages have words for Mile and Pound, Inch, the Dutch for inch is translated as thumb !
I tend to work in both, which ever is right for the job. I was lucky to come across a large quantity of NOS Mitutoyo instruments, both Imperial and metric, mikes up to 6″/ 150mm at £8 each, depth and verniers about £10, even a height gauge.
For Beeza650 I would remind him that old bikes and even some newer ones use 26 TPI Cycle thread in Imperial, but DO NOT confuse it with 26 TPI BSB, (British Standard Brass ). Good Luck Noel.