If you're more comfortable with Windows development than Linux development, it's a way to get things running more easily. (Although I expect that for many HN readers it's the other way around.)
I was wondering the same thing. Without a display or most other "Windows" type things, how do you work with a Pi running Windows? I'm guessing you have to be comfortable with the shell, which takes you one step out of Windows.
Plus, Microsoft seems to be big on cross compiling .NET code on Linux. Wouldn't it make more sense to load Linux on the Pi, develop in V.S., and cross compile it for Linux? Couldn't the V.S. team include a "Build to Linux" button that compiles the code and pushes it to an SSH target? That seems much better than dealing with embedded Windows.
The idea is to use the Pi as a device to which IoT-focused applications can be deployed after being developed on a Windows PC. For Windows-focused developers, it can be a gateway to building on an unfamiliar platform without abandoning the comfortable dev environment that they're already proficient with.
I would expect that Windows 10 could run proprietary stuff like Netflix DRM which would make it a good choice as a media station since Raspbian etc. can't run Netflix, but who knows.