Lack of focus has a real cost, even to large companies. It's the difference between polished slick software, and a design-by-committee mess.
Apple would very likely _love_ to have a second or third profit generator. If you examine the profits taken on iPads, MacBooks, and everything else Apple does (see http://www.asymco.com) relative to the iPhone, it is a one trick pony.
Hard to peel apart your "focus" when 85% of your business relies on it.
And I don't think they can really get by these days doing fewer things; I think they're right that an integrated ecosystem is the right answer, but part of that is, ecosystems are large. So they do need to do the more things, but they just don't seem to be doing the more things that well.
They have enough cash reserves to keep going for a long time, as well as other product lines that were successful enough to get them to where they are.