There isn't an Android desktop OS but rather Chrome OS and Chromebooks (the OS is essentially a browser).
It isn't just selling, it's sold out.
People don't really give a fuck about Windows anymore. Win8 sales figures have been really poor and most folks see no reason to upgrade. And apparently for those that do decide they want a new machine they're quite willing to go with Macbooks and Chromebooks.
There's how many Windows laptop models and how many Chromebook models?