OPEN QUESTION: Are Team Collaboration Tools mostly just glorified filesystems?

So it occured to me that every few years we reinvent the wheel in enterprise filesharing. Workgroups used to "collaborate" by dropping files into a shared network folder. Then there came Exchange Public Folders and Notes document libraries. Then there were complicated document management systems. Now there's Quickr and Sharepoint. The reality of the enterprise deployments I've seen of these applications is that most spaces are used primarily as glorified fileshares.* Essentially, aside from the versioning and locking (check in-check out) ability of these tools, they are being used to dump files, with the added bonus of being nicely integrated in to the productivity apps (Office, Outlook, Notes) in vogue. Which makes me wonder: Why haven't versioning filesystems become more popular for this sort of thing? I can easily envision an application that uses such a filesystem as the data store for an enterprise. Imagine for a moment what such an animal would look like: A filesystem that accounts for granular file permissions, versioning and file locking and is LDAP/enterprise directory-aware. You'd have the basis for perhaps 80% of the common usage of the aforementioned applications right there. Making good use of this versioning filesystem would basically entail a protocol implementing plugin. Such a system would remove a common dependency between messaging and collaboration that tends to cause frustrating vendor lock-in. Filesystems being what they are, HA and DR would probably also amount to a much simpler endeavor. I know of Wayback FS-which operates on top of traditional filesystems and proves my point that HA and DR should be a straightforward task- but I don't know of any commercial tools that implement a client for Wayback. Why hasn't this meme gained more traction?

*I'm not detracting from any of these products' ability to be so much more than glorified fileshares, just how they seem to be mostly used.