Legal departments also get in the way of contributions to open source. "We don't want any of our proprietary code to end up in that library" is a common theme found among legal teams that paint with too-broad of brushes. I am currently experiencing this.
Not to mention Microsoft is terrified, and I mean terrified of any open source code accidentally getting copypasted into some Windows or Office. A team I worked on there had to indirectly use linux and there was literally one designated person who was allowed to have a linux machine, and the machine had to be set up by a contractor whose job it was to ensure it was scrubbed of any source code before being handed over to the one guy who was actually allowed to touch it. I swear, you could make the lawyers jump a mile by sneaking up behind them and whispering "GPL"
Uh, this is Microsoft, they may have a slightly more close-minded view of the open source movement than, say RedHat or Google, or hell, even Oracle.