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.
in my opinion, companies like Apple don't need to accept payments using BTC, it would be better if the company as big as they make their own cryptocurrency and blockchain, because in my opinion it is more efficient and profitable for them. and moreover the cryptocurrency that they can directly connect to appstore and iTunes makes them more profitable.