Diminish routine requests: Most clients needs can be taken care of just with status and transportation/following information. Let the application handle these normal requests for you.
Boost client certainty: Customers that see you offer a request status query include on your shop will feel more sure and fulfilled that you are legitimate.
Customer account not needed: Customers don't have to have a record with your shop to see their request status. They can just enter their request # and email address.