Bijan Parsia posted an explanation of why academics don't publish online. It boils down to the fact that researchers in academia have to publish in refereed journals in order to get their jobs, and keep them. It's often much harder to get electronic rights back, partly because of publisher ignorance, traditional profits from microfilm and sales to libraries, and, more often now, future plans for CD or web versions of the journal. And so on.
Academic publishing can be a pretty ugly area, for a lot of different reasons.
This article on 'Academic Scholarship in the Digital Age' might also provide some clues as to why there is resistance to using online media to publish theses and dissertations. Despite all this, I have not yet heard anyone argue for publishing online on the basis that it give interested parties direct access to primary source information. Imagine that - research being used by regular people. I'd be curious to see if anything comes of it. Maybe someday people without access to an academic library will be able to check facts about global warming, among other things.