What the metric snobs fail to realize is how counter-intuitive the metric system is. Powers of ten is a wonderful idea, but it is only possible once you have divorced numbers from the real world. I mean, if you asked a caveman what two and two add up to, he'd probably say, "two what and two what?" As if two apples and two rabbits couldn't be added, because they were different things. The idea of "four" has to await the transition from seeing numbers as adjectives to seeing them as nouns in and of themselves.
In the meantime, when math is mostly done at the counting stage, you find certain numbers more handy (literally) than others. Five fingers make a hand, and then you have to start counting over. Four hands make twenty, and beyond that it's hard to hold numbers in your heads. So fives and twenties are very important to people whose primary job is to tally sheep or sacks of grain or game animals.
But when it comes time to share out amongst the clan what has been caught or gathered, then the number twelve becomes very important. Twelve can be evenly divided by two, three, four, and six, while ten is only divisible by two and five. For that matter, simple shape division -- as in, cutting a pie -- is easy to do in halves, thirds, fourths, and sixths. This is why the "dozen" is so important a number in various Indo-European languages. Secondarily, the principle that you can always cut something in half leads to a lot of things divided by two, four, eight, and sixteen.
The handiness of the dozen is why twelve is worked into a number of other systems. The Babylonians took the handy numbers twelve and five and decided that sixty would be a good, round number for large calculations. This is why there are sixty minutes in an hour, twenty-four hours in a day, and 360 degrees in a circle. Because when you're manipulating reality in an analog fashion -- making dials and doing geometry -- the number ten is a pain.
You try dividing a circle into ten equal sections by hand. For that matter, try dividing a ruler into tenths. Pick whatever base length (inch, centimeter, cashew nut -- make something up) you want. Now divide those base lengths into tenths. Make standard rulers in tenths of something so everyone can use them in their work. Go ahead. I'll wait.
Yes, the metric system makes a lot of calculations work out much faster. I'm glad the US adopted decimal currency back in the late 1700s. It is far easier than the British system of pounds, shillings, and pence, where there were twenty shillings in a pound and twelve pence in a shilling (and therefore 240 pence in a pound). But you can see why it was done that way: twelve pence is easier to portion out than ten pennies; meanwhile, if you think of money as actual objects (mounds of coins) rather than abstract numbers, then physically counting large amounts of money is easier if you do it by twenties. A pound of silver is the product of the two handiest large numbers to physically calculate with: a dozen and a score.
Meanwhile, the avoirdupois pound, where you're mostly weighing things out, wants an even scale. It uses the principle of division by halves. A pound is sixteen ounces, as is a pint (a pint's a pound the world around!). A pint = 2 cups of eight ounces each. A cup is divisible into sixteen Tablespoons (one half ounce each). Going the other way, two pints is a quart, four quarts is a gallon.
Is the Imperial system arbitrary? No. It is true to reality as it is found and experienced. The metric system is arbitrary, since it picks one number to use as the basis for all numbering. You think I'm wrong? Then why do computers work in binary rather than base 10? Why do we buy memory cards in 2GB, 4GB, 8GB? Because machines work in multiples of two, while we have chosen to work in multiples of ten. (The major alternative to base 2 in computer science is base 16, by the way, not base 10.) Yes, we find it easy to reckon in tens, but it's arbitrary. And it doesn't help you when you're doing ordinary tasks like portioning out food.
I'm not saying we should dump the metric system. I'm just saying that jerks who think the metric system is naturally superior are, well -- jerks.