Updating an internal document is an operation which should be very easy to all designers and to all managers, thus very fast. Why very easy? Simply to enforce implementation of latest changes in a managed way. This does not necessarily mean releasing or publishing the changes implemented, although it could. That means making the latest changes immediately available, and does not affect any of the previous versions which still are available, the way they previously were. Only centralized automatic versioning systems offer such flexibility.
Non versioned document bases actually only implement base size growth (i.e. creation from scratch), but not fast update (i.e. modification of existing documents), because version information is missing, and because documents are usually duplicated. Actually, non versioned document bases' hard copies are always duplicated, electronic non versioned copies are very often duplicated.