Metric sucks, and would fail without explicit government advocacy and support.  Case in point, most Americans grew up learning American Standard (very close to Imperial, but not quite) because all the adults used it, and also learned Metric in school, because the government wanted people to use it.  Most everyone, if they have a choice, prefer American Standard in regards to the kinds of useful metrics lay people use; i.e. miles for traveling distances, feet/yards for sight distances, and inches and fractions of inches for fine distances.  The fact that an adult can convert traveling distances (km) into sight distances (meters) in their head is generally a useless feature, because people rarely have any reason to do so.