The efforts by Microsoft should be seen in a different light I think. They have a product range that far exceeds the scope of the Android platform and the apps they develop on it. If anything, they want to stay in touch with their userbase. They are probably even willing to make a loss on the Android endeavour alone. Like you said, they have failed time and time again pushing their own Windows based operating systems. But of course they do want to keep a foot in the mobile market. That is the grounds upon which I develop apps for my company too. Not to make money off of those apps directly, but to be able to entice them to some other products and websites which are profitable for us.