Control procurement - Work performance data & report?

Can anyone explain as to why do we have work performance data and work performance report in control procurement as inputs?

Good stuff to review pmbook.

wpd shows the work results, including the supplier's contracted ones. Defects if any, changes and variances have to checked against contract conditions. If work is completed - it has to be paid

wpr may contain sipplier's parts which are defined in the contract Degree of work completion. If deadlines are missed - some penalties may apply or no fee awarded.