Sure, some mass produced items in Japan do use cheap foreign labor but it has not yet bled into their legendary craftsmanship industries.
It's the abuse of immigrant labor that's wrong.
Also, exploitation only applies if the workers 1) have no better option and 2) their options are artificially constrained by the party offering their only option. Anything else is simply failing to understand their situation.
Simply because they are abiding by minimum wage laws and making less than you are per hour does not mean they are exploited. Simply because Detroit is segregated in practice (as a result of factors beyond the control of most of the individuals) does not mean these workers are exploited. The fact that the dinosaurs went extinct even though they too, like us, deserve a chance to exist does not mean these workers were exploited.
Is theRe a historic reason for this, or example of schellings segregation model?
Again, see "sweatshops."
This has been going on for years in a number of countries (Spain, Italy, etc...) just so the goods can be marked "Made in *". The TV image of the careful old craftsman hand-sweing your luggage is a falsehood. It's sweatshops all over again.
It's even happening in the United States. Louis Vuitton does its repairs with immigrant labor in southern California so it can say the work was done in America. (The whole thing is tremendously complicated because of California laws about handbags and leather goods, but that's off topic.)
There are compounds in some states that are essentially isolated towns surrounding a factory where Chinese laborers put things together so they can be marked "Made in USA." The laborers eat, sleep, work, and live without ever going outside the compound. It's like the horror stories we see about China, but on U.S. soil.