That's because a canned, prescriptive checklist, like the QSA, is not an effective audit tool. People who use them tend not to deviate from the prescribed questions, therefore, there's no evaluation of the system, since it forces a 'yes' or 'no' answer. Auditing is, in reality, very rarely as cut and dried as yes, or no........
The AIAG noted this when the followed a number of QS-9000 audits and found that it was an ineffective tool. Hence it was withdrawn.