Well a lot of things people don't understand is that its not simply miles and feet.
It's even down to the liquid measurements and such that are not metric that are confusing such as,
quarts teaspoons tablespoons like do you know how many go in each?
No I bet you don't.
The reason our system was invented here in the US was to make the numbers smaller.
In the metric system anything less than 1 liter is measured in 1's so up to 999 u'd have to say 999 milliliters or 99.9 centiliters.
In the US we'd have a smaller integer for that or breaking pt.
It also comes easier to rounding when your talking about objects weight its easier to tell the weight of a person that's 150lbs than 45kg.
But when it comes to science, you almost need the metric system. Because its so precise.
Another popular belief is that US is against it, and it's not were trying to change. Scientifically we have been changed for years. If you learn any sciences in school you'll probably be using metric.
Science textbooks are almost entirely in metric.
Its just hard to change the US so fast, because education system is hard as it is. So, to change everything in one big swing is tough.
It's all being presented slowly at an easier pace.