Other than familiarity, what are the advantages of the english system of measurement?

It is a system of weights and measures that evolved over time and was once the de facto standard throughout much of the world. The best definition of this system comes with the British Weights and Measures Act of 1824.

You probably know that the English system of measurements holds few advantages. So why hasn't the U.S. converted? The primary advantage to hanging on to the English system is cost of conversion. For example, in 2009, NASA stated that the conversion of the space shuttle program to SI would cost $370 million. This was a price tag for which NASA simply did not have the funds. In another example, when Great Britain began to process for metrification in the 1990s, the estimated cost for changing all of its road signs was the equivalent of between $1.5 and $1.8 billion.

The second advantage of continuing with the English system is customary usage. For example, distances in football and baseball are closely linked to feet and yards, and decades of records are kept in these units. Cooking is another area where customary units in the U.S. are quarts, cups, ounces, pounds, etc. Finally, our culture is filled with sayings, such as, 'Give him an inch and he'll take a mile.' It just isn't the same to say, 'Give him 2.54 centimeters and he'll take 1.61 kilometers.'