When email archiving was first adopted by organizations an architecture that suited at the time would have been implemented.
But requirements change over time. The number of users being supported may have increased significantly for example, or perhaps new departments are also being archived.
And as manufacturers develop their software and hardware additional facilities may become available.
For example Enterprise Vault version 11 is way superior to older versions, and an implementation today may look very different from the way it would have been done under Enterprise Vault version 8.
The flexibility of ArchiveShuttle, and the fact that migration activities are transparent to users, mean that re-architecture projects can be undertaken without business disruption.