Microsoft Singularity : why closed
First you need to understand the goals of Microsoft Research.


  Our labs are unique among corporate research facilities in that they
  balance an open academic model with an effective process for building
  research results into product development. This approach, unique among
  corporate research facilities, pays off for Microsoft as enhancements
  to virtually every product and service it offers and as entirely new
  lines of business for the company. At the same time, it produces
  significant technological and intellectual advances across the
  spectrum of computer science.


from: Inventing the Future of Computing

Second you need to see how these ideas are translated into current projects.


  Windows 7. The latest version of Microsoft’s flagship operating system
  incorporates a number of “under the hood” technologies from Microsoft
  Research that contribute to the product’s improved performance,
  reliability and usability. These include enhancements to handwriting
  recognition, graphics performance, networking and security.
  Additionally, the product development team made use of a number of
  Microsoft Research technologies to write and test code efficiently and
  more thoroughly identify potential security issues.


See: Bringing Innovations to Life and Making Computers More Capable and Useful

Lastly you need to understand that Singularity has been used as a springboard for other projects:


  Microsoft describes Singularity as a research project "which
  demonstrated that modern programming languages and software
  engineering techniques could fundamentally improve software
  architectures." Singularity ended up spawning and/or influencing a
  number of other operating system research projects at Microsoft,
  including Barrelfish, Helios, Midori (Wikipedia) and Drawbridge.


from The father of Microsoft's Singularity OS moves on