The actual user preference for a particular measurement system (or individual unit) will often depend on the domain, i.e. the usage scenario. This is not something that system locales would currently record. However, these are some of the use cases that would need to be handled.
Travel
Distance on land: km vs. mi vs. mi&ft vs. mi&yd
Speed: km/h vs. m/s vs. mi/h vs. mph
Fuel efficiency: l/100 km vs. cl/km vs. km/l vs. gal/mi vs. mi/gal vs. l/mi vs mi/l
Weather
Temperature: °C vs. °F
Air pressure: hPa vs. Pa vs. bar vs. mbar vs. torr vs. mmHg
Wind speed: km/h vs. m/s vs. mi/h vs. mph vs. knot vs. Beaufort scale
Human body, health
Height: cm vs. m vs. ft&in vs. in
Weight: kg vs. lb vs. st&lb
Clothing: cm vs. in and overall a can of worms
Kitchen
Temperature: °C vs. °F vs. oven level
Solid measurement: weight vs. volume
Weight: kg vs. hg vs. dag vs. lb&oz
Volume: l vs. L vs. cm³ vs. ml vs. gal&qt&pt&oz (US vs. UK) vs. cup&tbs&…
Duration: min vs. h&min (1:23 vs. 1 h 23 min) vs. h
Food energy: kJ vs. kcal vs. Cal
Computer
Data size: kB vs. Kb vs. kbyte vs. Kbyte vs. KiB …
The actual user preference for a particular measurement system (or individual unit) will often depend on the domain, i.e. the usage scenario. This is not something that system locales would currently record. However, these are some of the use cases that would need to be handled.
1:23vs. 1h23min) vs. hPS: CLDR provides a good overview of local preferences: https://www.unicode.org/cldr/charts/latest/supplemental/unit_preferences.html