Why were alcoholic beverages sold by be fifth before metric?

Alcoholic beverages were not sold by fifths before metric. The fifth is a unit of measurement equal to one-fifth of a gallon, and it has been used in the United States since the 18th century. The metric system is a decimal system of measurement that was developed in France in the 18th century, and it is now used in most countries around the world. The fifth is not a metric unit of measurement, so alcoholic beverages were not sold by fifths before metric.