Because people needed to measure things - to trade for example, or so that rulers could judge the wealth of their subjects and so set tax levels.
The early measurement units were crude and based on readily available things.
metric and customary
the english system of measure
customary
metric
Alan Bercotti
Myanmar formerly known as Burma uses the imperial system of measurement. It used to be a British colony and has not yet adopted the metric system.
The customary system of measurement has evolved over time and does not have a specific inventor or creation date. It developed organically through everyday use and trade practices in various cultures before being standardized.
The united states used the customary system when the british brought here before the revoluitionary war. only the us, UK, myanmar, and Liberia still use the systems of measurement.
The United States customary system (also called American system or, sometimes, "English units") is the most commonly used system of measurement in the United States.
A Customary Unit or non-SI unit is a measurement unit that is not part of the metric system. Customary units are mainly units of the Imperial system but they could be localised customary units - such as Gaj (for area) is South Asia.
They are both systems of measurement except that the metric system is simpler and used by the majority of the world.
America uses the customary units f measurement.