Yup, Microsoft doesn't want to do it because they insist on changing Windows into something people can't use (pretty much the entire time Ballmer was in charge). Nadella seems to understand that it's not about Microsoft, it's about users. If Microsoft doesn't give what the users demand, their operating system market is going to collapse. That doesn't just apply to Windows, but also Windows Phone.
Speaking of which, I hope Nadella announces removing software constraints from Windows Phone and Windows RT soon. If you could customize said products the way you can customize Windows, Android would be in serious risk of getting crushed over the next decade.