When one label buys a catalogue from another label the purchasing label often has to replace the cover image – if only to replace the logo. As a consequence the release's identifier, be it a GRID or a UPC will change.
A DSP that has a commercial relationship with the selling and purchasing label is lucky enough: it could keep all the content available for its clients to enjoy (assuming appropriate deals, of course). But since the purchasing label has given the release a new ID, the DSP has no means to link the release as sent from the old owner to the release sent from the new owner.
As a consequence, all the auxiliary metadata that the DSP collected in the past is now gone. Worse, even, consumers who have bought access to the "old version" of the release find their access to be barred – while the release is still available (in it's new version). This is a very bad customer experience.
The Choreography for the Transfer of Catalogues between Rights Holders of Sound Recordings and other such Rights Holders defines the means of using the "normal" Release Delivery standards that allow:
As a consequence, a DSP can (i) plan a catalogue transfer and (ii) map the new ID to the old ID and the problems mentioned above can be avoided.