Well yes but those measurements are still "arbitrary" in the sense that they have no relation to anything that humans regularly deal with or have an intuition f

Well yes but those measurements are still "arbitrary" in the sense that they have no relation to anything that humans regularly deal with or have an intuition for. Basing a unit of measurement on the size of the Earth? Why not base it on the size of the Sun, or on the distance between Toronto and Timbuktu, or on the combined height of every member of the U.S congress if they all laid head to toe? Those numbers mean nothing to me, but I have a good intuitive feel for distances like "the general range of human heights", "the size of my foot", or "how far I can walk in an hour". Imperial measurements have their origins in those kind of intuitive, everyday quantities that we humans have a natural feel for; that's the sense in which they're not "arbitrary". That doesn't nmake imperial measurements unconditionally "better", it just makes them more useful and relatable in certain contexts.