Match Invoice to Receipt or PO?

Can someone explain the benefits of matching an invoice to a receipt vs. a PO?

So far I am thinking of the following Cons for matching invoices to receipts:

1. Any PO that is set to match invoice to receipt is not available to be invoiced through iSupplier Portal.

2. If accounting gets a paper invoice, they cannot enter it into AP because there is potentially no receipt to match to and they lose the ability to get a hold report.

Can anynone give me some Pros for matching to a receipt?

Thanks in advance!

Gary