Most of the time retailers do refunds back to original card number, or sometimes a store gift card (if for some reason that card has expired or something).

Occasionally I've had Costco refund me in cash, but they can see my entire order history because that's a membership store.

And they have a better handle on what's legit, and a generous return policy to begin with.

Medical Service Providers however have given check refunds for services prepaid for with cards, that ended being reimbursed (to the vendor) by the health care insurer.

I'm not sure why (and its not a real useful MS opportunity) but maybe its easier for their systems to handle it through an A/P process, rather than a customer refund process.

Or maybe they have some dollar threshold, and once the number is > $500 or what not, they require A/P to be involved.