If you take in account that the public company works in their shareholders best interest, i would say it is done with silent approval of shareholders. Ugly, mutated form of slavery.
Shareholders -> Apple -/-> Wistron -> underpaid labor.
(Edit: Wistron's shareholders? Sure. I didn't realize it was a public company or that parent comment was talking about it.)
So Shareholders -> Wistron -> underpaid labor.