Apple doesn't make developers do anything. Developers write apps for their platform because it is the one where consumers want to spend their money. They do this by being mean to developers, or, rather, not allowing developers to be mean to customers. It's the same way that apple leans hard on their suppliers but at the end of the day it has led to creating a healthy and wealthy ecosystem that those developers and suppliers still seem to contribute apps to.
Not protecting Foxconn, but I suggest you to compare their work conditions with other Chinese companies, where the competing mobile devices are manufactured. Problem is China and its borderline slavery labor conditions.
Thankfully, Apple started moving out to India and Vietnam.
