Why do you think Microsoft continues to develop Windows Phone?
You should follow this tweeter discussion from Sinofsky
https://twitter.com/stevesi/status/733699065763004416
It wasn't the difference between desktop and mobile stacks that pushed most away, rather the breaking changes between WP 7, WP 8, WP 8.1 and WP 10. As explained recently on the Ars Technica article,
http://arstechnica.com/information-technology/2016/05/onecor...
And as a developer I cannot really get why WP 10 is still so buggy (according to the reports) versus the already stable 8.1.
Microsoft eliminated QA as a job role and laid off all of its QA staff in 2014, with rather predictable consequences for both Windows 10 and WP 10. Plenty of articles about it if you Google around.
If anything, it's surprising that things have turned out as well for them as they have.
It does make sense, though. QA teams cost a lot of money, and don't produce anything at all. They're a cost center. The only thing they do is keep your quality up so that customers don't get mad and leave.
MS doesn't have to worry about that. People weren't buying WinPhone anyway, and no one's going to abandon Windows (PC OS) because of bugginess. So using the users as beta-testers makes perfect sense for them. If you don't like it, then don't buy MS products.
Remember any of these: Pocket PC, Windows CE, Microsoft Kin, Windows Embedded Handheld, ....
MS spent $1 billion for Kin alone. When they consider market to be important to their future, they'll keep going and spending money. Setbacks destroy their partners but they just wait and try again when time is right.
MS is still mainly business and OEM sales company. Consumer-centric divisions (including XBox, Windows Phone, Bing) are irrelevant from a profit standpoint. MS is perceptually trying to get into mobile because they are fearing for their business and OEM sales if they don't have the presense in mobile.
Useless product, nobody uses it, but the fact that they kept investing in it made most competitors lose their nerve.