I really don't see why the metric system is so inherently superior in non-scientific use.
It's just simpler and more intuitive.
Do you know off the top of your head how many feet make up half a mile, and how many meters make up half a kilometer? Which one is simpler to do in your head when needed? 2640. The math isn't hard. But conversion isn't the most important part of measurement. Units should be valuable in themselves. I have an idea of how long half a mile is in experiential terms in a way that I don't for half a kilometer, so changing to metric length units would take a considerable mental and even kinesthetic adjustment.
3 teaspoons in a tablespoon. Again, the main importance here is that teaspoons and tablespoons are things people use anyway in real life. I don't know off hand how many tablespoons are in a fluid once, but the others I've known since I was in kindergarten and it's not difficult if you take the time to learn it and will save you a lot of trouble. Fluid measurements are based on multiples of 2: 8 floz in a cup, 2 cups in a pint, 2 pints in a quart, 4 quarts in a gallon. Doubling an object (as opposed to multiplying an abstract number) is much easier than multiplying an object by ten (is there even a word for that? double quintupling?).
