These Android manufacturers are generally not just shipping vanilla Android and have development costs on top of patents and licensing. They do this because ow

These Android manufacturers are generally not just shipping vanilla Android and have development costs on top of patents and licensing. They do this because owning the software stack gives power, and they believe it distinguishes them (although usually makes the product worse than stock Android). Microsoft want to own the software stack so shipping Windows on Nokia phones makes sense. It wouldn't make sense for other manufacturers unless they don't mind loosing power over the stack (which Samsung, Huawei, Amazon etc. don't want). I agree with your points regarding limitations with Windows Phone. Just because an opportunity exists doesn't mean that they will succeed. Although I am unconvinced that the app market is that important. A few key apps are important, but Android app purchases lag heavily behind iPhone, and it is reasonable to suggest that feature phone users will lag even further (especially without a locally integrated payment system in developing markets).