Why is Outlook 2011 Database file not backed up by Time Machine?

Hello,

Why is Outlook 2011 for Mac 'Database' file located in:

Documents > Microsoft User Data > Office 2011 Identities > Main Identity

NOT backed up by Time Machine?

This is the first time I have ever encountered a file not backed up by Time Machine??   I have no restrictions to prevent that happening.

All the records in:

Documents > Microsoft User Data > Office 2011 Identities > Main Identity > DATA RECORDS

ARE backed up

but NOT the DATABASE file under > Main Identity.

This has made Time Machine effectively useless to rely upon for backups of Office as you have to rebuild the identity from a Time Machine backup (which does not work in my case).

So now I am having to manually backup my Main Identity file every day so that I can restore from it if there is another crash in my Outlook 2011, which seems unbelievably ridiculous because this DATABASE file can simply be copied from a backup into the Main Identity again and it works.   So why won't Time Machine do the same and back it up and restore in the same manner?

Kind regards,

Mike