Instead of using GR/IR clearing account why cant we use provision for sundry creditors, if yes then why SAP using GR/IR Clearing Account

SAP uses the GRIR clearing a/c as it doesnt want to accept 
a liability by crediting the vendor a/c.A liability can be 
accepted only when the goods have been recieved and the 
invoice checked.When the invoice is recieved, GRIR is 
debited, the vendor a/c is credited & thus we can accept 
liability with the vendor.