The USA is one of three countries who do not use the metric system of measure. We use a system that makes little sense. We hold on to our Imperial system of measure for what reason? Perhaps because as a country we don't like change? There is no benefit to using Imperial over Metric. Metric is a natural, easy to understand, scale-able measurement system. The Imperial system we use today is confusing and not based in reality.
12 inches to a foot; 3 feet to a yard (which is almost a meter); 5,280 feet in a mile...etc.
10 millimeters to a centimeter; 100 centimeters to a meter; 1,000 meters to a kilometer...etc. Metric units are based on the number 10 which makes it easy to convert between units.