Cause 1:

If versioning is enabled in SharePoint , then the SharePoint Archiving Policy must be set to prune documents in order to realize any reduction in database size.

With pruning disabled, the Enterprise Vault Shortcut becomes the newest version of the document (file) and SharePoint continues to store the older versions in the content database.

Cause 2:

The time period defined in the SharePoint policy for items to remain unmodified before being replaced by shortcuts has not yet elapsed, or if the Vault Store hosting the SharePoint archives has the Remove Safety Copies setting set to "After Backup" then the vault store partitions for this Vault Store may not yet have been backed up.  Without the items having been confirmed to have been backed up, Enterprise Vault will not remove the originals from SharePoint and replace them with shortcuts.

Solution 1:

Enable pruning in the SharePoint Archiving policy and set the number of versions to retain. The number of full items (i.e., not counting the EV shortcut) left in SharePoint's content database will always be one less than the value set for pruning.

For example, setting the pruning value to 1 will cause only the EV shortcut to be left in SharePoint and all older versions of the file will be archived and removed. Setting the pruning value to 2 will cause the EV shortcut and one older version to remain in SharePoint. Setting it to 3 will leave the shortcut and two older versions, and so on. The upshot is that disabling pruning or setting it to any value greater than 1 will result in some document versions being kept in the SharePoint content database, so set the value to 1 for maximal database shrinkage.

Note:  Pruning only applies to documents that have been archived.

Solution 2:

Review the "Remove unmodified items older than:" setting in the SharePoint Policy and verify that the EV partitions have been successfully backed up.