Re: M$ should be paying us!
The OS is an end unto itself for Microsoft. Microsoft needs Windows to keep reminding users why they are using Windows. With Win 10, it is also a platform to mine user data, and embed cloud hooks into the OS. It's also about the 'ecosystem', which requires a Microsoft account to partake in.
It's not due to an economic or technical reason why Win 10 is the way it is now. It's due to a political reason: a response to Apple and Google's encroachment with their mobile duopoly, and paranoia brought on by years of declining PC sales.