If you try to use your open-loop (Amex, Visa, Mastercard) gift card for certain purchases, you will find out just how futile it can be. The problem is that certain retailers will routinely try to authorize a certain amount just to pre-validate the card. For instance, if you want to use your card at the pump to buy gas, the pump will authorize $50 or $75 just to allow you to use the card, so if you have a card that is only worth $25, there is no way it will get accepted. People don’t notice this with credit or debit cards because they typically have a much higher credit limit or balance so it is never a problem. Restaurants also typically do this when running your card to leave extra room for a tip, even if you tell them to put a certain amount on the card.