The differences in development environment aren't as important as the money factor, for me. Apple's market consists mainly of people willing and able to pay the premium for associating with the Apple brand, and consequently it's a no-brainer to publish apps on that platform.

Edit: I also don't write apps that involve very specific use cases for hardware; my apps are utilities and entertainment (games). Consequently the differences in environments are actually quite trivial. I can easily control for "fragmentation" on Android by targeting 4.0 or later, which serves the majority of Android phones, in a (mostly) uniform way.

How are these problems any different from developing for PCs?

Because, Microsoft and even linux have hardware abstractions that mostly conform to a spec. The spec in Android is complete crap and largely ignored by the hardware vendors. In Windows and linux you get the complete OS from the OS owner (MS, or ubuntu or red hat etc...) and each driver has to match the spec exactly or the driver will fail, with Android you are getting custom forks of the OS. Each one is customized to the hardware and has a different behavior.

In short it's MUCH easier to support different hardware in the PC world because the OS vendors have standardized the specs and in Android it's very wild west, each hardware vendor is supplying their own version of Android which is mostly the same but has subtle but key differences.