My company uses subversion for *all* documents, not just software development ones. The corporate documents repository has no branches.
This essentially meets the requirements for document management for ISO9000.
ISO9000 auditors are business people, not IT people.
Even if we had a perfect workflow for controlling distribution, generation and modification of documents, it would be still *much* harder to convince an ISO9000 auditor of this if we were using a DVCS.
I think this is the nature of why a number of companies are still very interested in centralised version control.