University IT policies have many many stakeholders (Provosts, Regents, President, Deans, department heads, just to name a few) and a lot of interdepartmental politicking needs to be taken into account.
The Provosts, Regents, President, Deans, and department heads of my institution are concerned that they can get and send email, that neither the administration stuff nor the website is hacked, that no screw-up risks escalation to a PR disaster, and that it doesn't all cost too much. And that other people don't bitch about it, and all in all that it can be left to run itself -- because they have more than enough other, IT-unrelated concerns of their own. As long as they can plug their own laptops into the LAN they don't care what hardware or software the masses are using.
In the relevant committees, you're likely to find deep conservatism, even from people who themselves use Gentoo or whatever. Elementary classes in "computer literacy" are likely to be in mere secretarial skills, and their teachers can argue for MS software on Windows as they can truthfully say that this is near ubiquitous in the corporate world. Students and staff want to use software with which they're already familiar, which for the huge majority will mean MS software. Staff find it easier to tell people who are mystified by spreadsheet problems to look up the matter in an actual book on Excel than to do so in a non-existent book on Gnumeric. Still, there's no reason not to install FOSS in addition to the shrinkwrapped stuff, and so my institution has OOo, Gimp, etc sitting unopened on just about all of its computers.