If logging via the portal the customer raises a service action.  If the customer is phoning the service desk the analyst has to select from the workflow options and cannot record the action that is relevant.  The only way to raise a SA request/call in the core application is to do so via a CMDB search.  Adding in a quick way to access the action menu for analysts would provide SD a consistent flow for all calls/requests if using the service catalog extensively.
It would also ensure that the reporting would be consistent regardless of logging method