I think the only reason to ask for a card type is to discourage customers from trying to pay with an unsupported one. Merchants can still be charged fees for de

I think the only reason to ask for a card type is to discourage customers from trying to pay with an unsupported one. Merchants can still be charged fees for declined transactions. A few of the larger merchants can benefit from choosing a different transaction acquirer based on card type (e.g. lower fees for Amex) but they should not trust the card type selected by the customer.