Why do metric sockets come in 1/4", 3/8" and 1/2" drive?

[MinnesotaEric]

Why don't they come in metric measurement drives in countries that use the metric system?

As I heard it, it is because English and USA machine tools all used the inch system and post-war foreign toolmakers used SAE and British Imperial System machine tools since we'd blown to smithereens the German and Japanese machine tools.

 

[airbiscuit]

Machine Tools of today like working in the metric system. Everything is orderly in factors of 10.

 

[airbiscuit]

I have some tape measures that have both inch and metric scales on them. Occasionally, I'll use the metric scale because it is quicker and easier to divide in half or some other fraction.