Although their primary function is to provide credit to customers, credit cards issued by various banks do differ in certain aspects or attributes. These attributes can be one or more of the following: credit limits, rate of interest, and many others.
Most cards impure certain transaction or transfer fees on every transaction, or transfer of a certain amount of money. Initially, all the companies introduced the concept of zero balance transfer. This was basically to lure the customers into applying for their cards and this offer was to be valid only up to a certain period of time after the card was issued. But what many people did was, they used it until it's zero balance transfer was valid and once the validity of the offer expired, they switched to other banks which provided similar schemes. In this way, the entire idea was disrupted. And the companies felt cheated.
Here, the banks have now stopped issuing the zero balance transfer scheme. One of the major banks started imposing a fee on every transfer of money. Many other banks followed suit, and now a major of the banks are imposing transfer fees. Many people also used them under this scheme to wipe off their debts.
Using these cards, mean paying lower interest rates, and as a result people used multiple cards to transfer their own amount into the account of this credit card for transfer to others which made it difficult for the banks to manage, as the cards were their major source of income. The rate of interest was drastically cut down. Thus, this scheme kind of back fired toward the banks. This is the main reason why cards under this offer are available only to genuine customers with good credit ratings.