There isn't a whole lot in there for them. Margins are thin and their hardware is no longer unique since they are using the same Intel CPUs that everyone else uses. Apple almost certainly makes more money on iPhones and tablets than they do on PCs and laptops; I and others expect that they will transition from selling PC and everything else to selling everything else and software.
Well, how do you expect developers to write apps for iOS to do? Move to Windows?
And while the PC market is "bad", you have to realize Apple still moves millions of Macs every year - it may not be the most profitable line, but it still makes money (more than iTunes revenue does, though Apple tries to keep that one down since they want to sell content to move hardware).
It's also interesting how people claim Apple will kill off the PC, and that the "Post PC" era means that. No, the Post-PC era means the PC as the central unit of computing is over. PCs will be around, just there will be more varied computing devices around, from smartphones, tablets, laptops, desktops, and other things. Which one you pick depends on the intended activity. Instead of households needing 1 PC per family member, it's decreased to 1 (or 2) shared PC while everyone uses a tablet and smartphone. Heck, remember netbooks? They were a stopgap measure that people used so they could avoid having to take turns at the PC.
Desktop PCs have moved out from the realm of the way to get a super cheap PC to the realm of enthusiast PCs - they're no longer the cheapest computing option, but they still remain the option of choice if you want high end computing. Which is fine - as the market changes niches evolve. Laptops are cheap and plentiful (see Best Buy) and if you need a PC for home, they're the preferred option - they're small, portable, look clean on the desk, are powerful enough and external expansion makes overcoming their limitations trivially easy.
Apple's worst performing product line is the iPod, for obvious reasons - they don't move much, they don't make much. Even they make more money than iTunes. Macs are a staple at Apple, and while I see them cutting down the number of models they offer in the near future, they'll still offer them for a long time to come. The PC market won't disappear - it's just less important nowadays than it was in the past.