Ounces and pounds are convenient units for ingredients in recipes. Grams are very small, kilograms inconveniently large. Pints are more reasonable than litres.

The imperial system was designed for everyday use, rather than for convenience in scientific calculations.

The units of temperature on the Fahrenheit Scale are smaller, and therefore give a better indication of air temperature without needing to resort to decimals.

The fact that there are 16 ounces in a pound, 14 pounds in a stone, 3 feet in a yard, and so on, meant that people learning maths 50 years ago became competent in dealing with units to bases other than 10. Now this is not routinely taught, many youngsters have trouble doing arithmetic on the one non-metric unit still in use — time.

The only advantage to the system we use here in America is that we already know it and that we are too lazy in general to learn/adapt to something new.

Metric system is a a new system and is now accepted in many countries.