Alternative take: the US customary units have stuck around because SI has failed to present itself as better enough to switch. Grant that all base units are arb

Alternative take: the US customary units have stuck around because SI has failed to present itself as better enough to switch. Grant that all base units are arbitrary[1], many of the customary units make easier logical sense in day-to-day life, or are designed to be divisible in easier units than SI units are designed to be. Do you want ⅓ of a foot? Well, that's 4 inches (12 inches in a foot, divide by 3, you get 4). Feet are made up of 12 inches, a number that can be divided by 2, 3, 4, and 6. Very convenient. One yard is three feet, gaining all the divisibility benefits that feet already have, and then some. How about volume? Especially when dealing with recipes, the customary units are extremely convenient, with perhaps one exception. One gallon is four quarts (alternatively, two pottles, but that unit is not encountered much, shame), one quart is two pints, one pint is two cups, one cup is eight fluid ounces, one fluid ounce is two tablespoons, one tablespoon is three teaspoons. Excepting the last one (three instead of two), these measures make it very easy to double and halve quantities at will. Just a little bit of math, and third and quarter measurements are not difficult either. Effectively the customary volume measurements are counting in binary. How about temperature? What's a more convenient scale for human living conditions? 0–100 °F or -20–40 °C? I know what one I'd pick. I am aware people live in even colder and hotter environments, but the majority of people in the world don't need to worry about values outside of this range. I also think "0 is very cold" and "100 is very hot" just makes more sense than "-20 is very cold" and "40 is very hot". Metric/SI systems have been pushed in the United States since the 1860s. The continued use of the customary units is not for lack of trying. The customary units are plenty good already, have a few advantages of their own, and SI has failed to present itself as an overall better system. We'd probably adapt just fine, but we don't want to. We already have a convenient system for everyday use. (SI is probably better in scientific fields, and it's already used in such industry, so there you go.) [1] Yes, even the SI base units. Look up their definitions and they're all defined with very difficult to remember numbers that you can measure against physical constants. This is because old meters, grams, liters, et al were arbitrary things and physical constant definitions have been retrofitted onto them. United States customary units are likewise defined as multiplications against the SI base units. Customary units already benefit from the physical constant definitions.