Because it's much, much easier and quicker to run most builds in the simulator, especially when you're not dealing with something that has a tricky performance point to balance. At least with the iOS simulator, it makes debugging low memory warnings and secondary screens much easier as well.
Depends on what you're developing. Frequently you develop in parallel for the desktop and your console of choice, when you're doing non-performance-intensive stuff. This is especially true of XNA and the like, where your code is identical.
What I mean is you don't compile and run it on your PC, then run it in a PS3 emulator. You run it on a PS3 dev machine.
iPhone, Xbox, PS3 are platforms do not have much hardware difference device. But Android supported tons of devices, without a nice emulator sometime you dun know is it your phone(if you test on real device) causing problems or your code.
I don't know what you mean. I developed a 3D game for Android and never had a problem with my "phone causing problems", or any other phones really besides extremely rare crashes from my crash reporter once it was released.