Corporations are, like Westphalian nation-states, explicitly amoral entities. The extent to which they behave morally is due to market and/or political pressure, not any inherent moral judgement.
Apple makes consumer devices. That's their business. They have a responsibility to make the greatest possible profit selling those devices. That's where their responsibility begins and ends.
Now, there are all sorts of moral dimensions that can affect their decisions. If their phones were made with slave labour, people might not buy them and talent might not want to work for them. But the reason Apple doesn't employ slave labour isn't because it is a moral entity; it isn't. Apple doesn't employ slave labour because doing so would hurt its bottom line.
If you want companies to behave in an ethical fashion, you need to align legal, social, market, tax, and other incentives in order to push them in that direction. Expecting them to do so out of the goodness of their hearts is quixotic: they have no hearts with which to be good.