Then they could just demand they get a cut of every transaction. Also, you can do homebanking on your iPhone (I assume, I use Android), and Apple doesn't want a cut on every wire transfer you initiate.
If I had to guess, I'd say there is just a gentlemen's agreement between the powers that be and Apple (and other companies) to keep Bitcoin down.
As someone mentioned above Coinjar is still available on the store.
It is far more likely that Apple simply doesn't want to be associated with Bitcoin wallets which historically have a very high likelihood of people losing money.
The banking example is really great. Same goes for Venmo, Square, etc. Apple doesn't get a cut of those transactions, so the dispute must lie somewhere else.
If I had to guess, I'd say there is just a gentlemen's agreement between the powers that be and Apple (and other companies) to keep Bitcoin down.