Hey Greg,
I guess you just made Gary's point quite well. Metrication is a world standard, whereas in some parts of the world F/P/S is not. For instance, to me here in Canada, only one of your answers is correct. "Inches in a mile is rather a useless number." That's true!! (Unless you're recently working on Doug Gonz's mutter-byke speedometer or gearing!!)
But there are 69.355 CI in a Gallon here. And even in the US, there are two different sizes of a quart.... liquid and dry...which are different.
And there are 277.419 CI in a gallon, except in the US there are again two other answers.
Other than it's easier, that's what metrification is attempting to correct. Make it so we all have a common ground. Apples and apples. Won't happen in your life-time or mine, but it will happen eventually. US industry is WELL on its way, for a number of years now. Although I've got to admit that metrification in Canada is certainly taking more than one generation to complete. But my 30-something son sure knows roughly how long a metre is, and roughly how much a kilo weighs, and can put about a litre of water in the soup pot Ok without wrecking the broth. Not by "measured standards", but just by holding out his arms, or picking something up, or looking at a variety of containers. He's no more accurate at it than I am at judging 3 feet, or 2 pounds, or a quart (although even I can tell a US quart from a Canadian quart, but much harder to see the difference between a US quart and a liter... not so easy with gallon though, unless they are sitting side-by-side). But he can't gap his thumb and finger at 1/16", and for sure can't do 0.0625", but he's not bad at 10mm.
Take care.
Brian Laws>