It's getting harder for them to find good engineers
Apple, particularly since the second coming of Jobs, has gradually alienated engineers. Back then, you could buy an Apple and you always had the sense of it being a bit over-engineered and well made, with decisions being taken (like the PPC) for rational reasons, or at least because of a certain element of beauty. At least the hardware architecture was a thing of beauty.
Now with Jobs, we get locked down boot loaders and operating systems. We get devices which are so badly designed you cannot even replace a broken battery. You can only install one operating system, the one that shipped with it. And that operating system was dumbed down to a point I cannot do anything useful with it as an engineer.
For engineers Apple has just become one of the worse consumer electronics companies. It feels like, at Apple you'll only be able to design products deliberately made bad by management decisions and you are not allowed to make it as good as you could. Working at a company which is like that, I know how frustrating that can be. All the interesting stuff inside that device, like for example the GSM/UMTS/LTE baseband has been outsourced to other companies. (there's only a tiny hand-full of baseband stacks, made by very few companies)
So Apple is no longer a place I'd like to work as an engineer. Luckily for Apple, since they have transcended into a religion, product quality doesn't matter anymore.