When we as consumers purchase something using a credit or debit card, a hold is immediately put on those funds in the consumer's account. Upon settling, which merchants typically do nightly, the money is permanently given to the merchant and funds taken from the consumer's account.
When a refund is requested, as many can attest, consumers are told it may take 10-15 days for the refund to be processed. During this time, the consumer continues to pay interest on the money, when charged to a credit card, or in the case of a debit card, does not have access to the funds until the refund settles through the credit/debit system.
Merchants take the money from us immediately and should be required to return it immediately upon granting a refund.