Well, the metre and the yard are within 10% of each other. Why is is the foot better adapted to human measurements than the yard? Why should people be 6 feet tall rather than two yards tall?

Then, you're picking the centimetre and the metre which are a factor of 100 apart, compared to the inch and the foot which are a factor of 12 apart. You forget the decimetre (10cm) which is about halfway between the inch and the foot (one decimetre = 4 inches, one foot = 3 decimetres) just like the foot is halfway between the decimetre and the metre (almost exactly halfway between the decimetre and the yard).

The centimetre is like the half-inch. I don't see why one unit should be better than the other in an absolute sense. This is all a bunch of rationalisations for preferences based on familiarity.

The basis for the meter was intended to be a sub-division of the circumference of the Earth, but turned out to be off significantly.

Huh? The metre is not significantly off the 10-millionth part of the distance from pole to equator (it's off only by about 0.02% !!) and the order of magnitude has been known since Eratosthenes in the 2rd century BC to within a few percent.

En un viejo país ineficiente, algo así como España entre dos guerras civiles, poseer una casa y poca hacienda y memoria ninguna. -- Gil de Biedma