How many of those units are really used?

Ex: Area: square inch, square foot, square yard, acre,
square mile, township, square fathom, square rod, square furlong,
square league, square mil, square pole, square perch, square hand,
square link, square chain

Only four of those are used. And in the dumbass metric system,
one can never decide if they should use square millimeters,
centimeters or meters when dealing with a small area.

also, ask a carpenter or a pastry chef if they would rather use
the metric system or the American system. Those guys do nothing but
use measurements all day, and I guarantee you they all use the
American system.