For those who prefer signature-based transactions for their debit cards, Amazon has a setting to have them run your debit card as credit.
You can do so here.
I’d imagine it’s useful for those who don’t have an alternative to using a PPDMC, etc., or for those who have some checking account bonus tied to having a certain number of signature-based transactions. For me, it’s useful for Provident CU ’round-up’ matching (Doctor of Credit has a particularly good resource).