Had they shipped Astoria in Windows 10 to allow Android apps to "just work" it would have destroyed their UWP strategy.
So they might get a few more Windows Phone users but they would have lost control of the new development platform and given it to Google on a silver platter. And they would never have got anywhere near the numbers Android is at.
I would be shocked if Microsoft don't bring UWP to macOS, Linux and Android (I don't see how they can with iOS) in the not-too-distant-future.
Kind of like how OS/2 support of Windows applications helped destroy it?
Would be nice to see Apps from VS running in Linux and macOS. There's been some effort that one assumes supports this direction... Also, all things to make Azure nicer to use and better as a target are in their long term interest.
My question mark over iOS is because of how strict Apple are with approved apps. Will Apple like Microsoft bringing "app parity" into the iOS eco-system and more importantly will they allow it?
That being said, it is pretty obvious it is a minuscule platform; apps are often lagging behind their iOS/Android counterparts, and there are some obvious ones missing (like Snapchat and Pokemon Go).
It is kind of sad really; I think it would be healthy with more than two major players, and Windows 10 users will probably feel quite at home in Windows 10 Mobile.