See the first 4 digits on a credit card? That's the BIN (Bank Identifier Number), it allows you to know who issued the car. You can tell if it's a gift card,

See the first 4 digits on a credit card? That's the BIN (Bank Identifier Number), it allows you to know who issued the car. You can tell if it's a gift card, prepaid cards. If you offer online service where you really need to know who the owner is, you clearly don't want such cards. Imagine someone setup a server offering illegal services, you can't identify the owner if the use such a card. If you offer metered based services where the user get's billed afterwards per usage, then you also don't want such cards since the person can use more and you won't be able to go after them. This is why such cards are banned.