@freemo you say proper precision and grading, but that's the whole point: in so many real world applications we find that the precision and grading isn't the most convenient for the work in front of us.
Say you're aligning a platform by eye, see that you need to raise it by about the length of your thumb, so you call out to the lift operator to raise it by a quantized amount.
"Two inches" happens to be a pretty convenient call out rather than "five centimeters" or, heaven forbid, "fifty millimeters."
It's simply more intuitive at common human scales.
Or, to put it another way, they're big and bulky, which is perfect for dealing with big and bulky human scale tasks!