The payment term in the item is ignored in sales orders and Invoices from AR

Summary:

The Payment terms attribute in the Item specifications is not taking it into a sales order, or an AR invoice.

Content:

For sales orders, the payment term is taken from the customer's site. And if the customer does not have a payment term configured, the sales order ignores the payment term placed on the item, and must be added manually to the order.

On an AR invoice, when the item is added with the payment term defined in its specifications, the invoice ignores it and the payment term field remains empty on the invoice

What function does the payment terms from the item serve if it apparently is not a default value in AR sales orders and invoices?