Everything has a cost. NASA estimated their cost was $370 million to switch to metric. https://www.cnbc.com/2015/06/04/why-the-us-hasnt-fully-adopted-the-metr

Everything has a cost. NASA estimated their cost was $370 million to switch to metric. https://www.cnbc.com/2015/06/04/why-the-us-hasnt-fully-adopted-the-metric-system.html https://www.cnbc.com/2015/06/04/why-the-us-hasnt-fully-adopt... The cost of switching road signs alone was quite expensive. Exit numbers, for example, are often the mile marker number.