Why is it not permitted to drive a vehicle with the old licence until the new document is received?

In the case of the replacement of a driving licence with the status “Valid”, where the applicant for the service requests that its validity be maintained during the period in which the new driving licence is being issued, if its expiry date does not fall due, the first one is cancelled, from “Valid” to “Cancelled, returned to the holder”, at the moment of handing over the new driving licence, whose status changes from “Issued” to “Valid”.