The system does not allow you to delete an un-used financial dimension in a gold build system once it has been created and activated in an account structure. Once this happens records are created in the DIMENSIONATTRIBUTESET & DIMENSIONATTRIBUTESETITEM tables irrespective if the dimension has been transacted on.

As the configuration of a system evolves throughout the lifecycle of a project it means that orphaned records are left in your gold build (and production system once it has been copied) if you no longer want to use that dimension.