When they really need to. But they'll fight it hard! Apple's business model is to lock everything down -- very closed indeed. This does not align with the goals of bitcoin, at least, how I perceive them.
tl;dr Apple = closed. BTC = open.
I guess they are still observing on samsung company that has been reported that they accept cryptocurrency specifically bitcoin as a form of payment. As we all know that a business should not rush things just because the other company had already in the system. Just like nokia now where in it was left behind by other smartphones when it comes to sales and upgrades.