Comment by genewitch

I forgot one thing. you said "why not have in^2 and in^3" we do, but we don't use that very often. Older American "muscle cars" engines' displacement was measured in cubic inches. every child learns what a square inch is. a "board foot" is 12 cubic inches of milled wood, 12 in^3 - I don't know how to verify this on a Sunday, so this may be wrong, the board-foot. And then, we use square feet; for floor space in a house, say, my house is ~1500 ft^2. We also use cubic yards, yd^3, for stuff like dirt, concrete. when talking about this, like if i need a driveway's worth of concrete, the load is measured in "yards" which is short for "cubic yards."

But all that aside, and with apologies to mods and you for sneering; i wanted to say this in my prior reply but when reading it aloud to my wife i took it out:

Americans can, in general, divide and multiply by numbers other than 10.

yes, we use acres and hectares, too! it sounds better to say i live on 6.5 acres to an American neighbor who asks, than 0.02630457km^2...