Accure Recipt check under the PO Shipment is disable in few cases and in few it is not though Purcha

 Hi All, 
I am unable to understand why this is happening for all the Inventory Nature (Stockable Items ) the under the PO the Accure Receipt check is enable while creating the PO but for all the Expense Nature of Items it is not ? 

I am not getting why is happening for all the expense Items ? 

IF I have defined the Accure on Receipt under the Purchasiing Option and Accural Expense Account as well then why this is happening ? 

Regrads, 
Mohammad Younus