The niche of Intel Joule is the capability of running Windows, and the power of Windows is you can develop on one computer, and run on another one with no libraries or whatsoever installed. Just copy and paste, no apt-get, no ldconfig.
That's actually the problem. A lot of people believed exactly this - and then they discovered that that "full Windows" is in fact Windows 10 IoT Core - which doesn't even have a gui and many standard APIs don't work there because it is a Windows UWP platform, not normal "desktop" Win32. A totally locked down sandbox using its own incompatible set of APIs. Essentially what the Hololens is running. Standard "desktop" Windows doesn't run on it and neither do standard applications (not even .NET stuff unless it is specifically targeting UWP). For all practical needs and purposes it is a completely different OS (think Windows Phone vs. normal Windows).
It is the same idiocy as to what Microsoft did with their Windows RT - there they have also claimed that it "runs Windows" so everyone expected their Windows applications to work on it. Except they didn't - ARM CPUs, totally locked down system.
If you have to deal with UWP and port/write everything from scratch, you can run Linux as well - and then Joule has no advantage over the common ARM boards. You even have to cross-compile, either for ARM or Windows, because apps for UWP need to be built in a special way, you certainly can't just "copy & paste" (first hand experience building apps for Hololens here ...).
This is pretty much a "me too" effort from Microsoft and Intel so that they can claim in their marketing that they are supporting the IoT that nobody has bought into, apart from a few very niche applications.