They're called secured cards, and they're very common. My first card was secured, it's a way to get access to a functional credit card (purchase protection, credit reporting, etc) with bad or non-existing credit.
The 2nd to last paragraph in that section starts with: "Secured credit cards are an option to allow a person with a poor credit history or no credit history to have a credit card which might not otherwise be available."
My first credit card was a secured VISA card and it had a high interest APR of 21%. The high interest rate was irrelevant to me. What was most important was that I had a credit card at all. When I got the card, I remembered the first thing I did was order music CDs from the web. This level of convenience wasn't possible by mailing in money orders. Since I paid off the full balance every month, whatever high interest rate the card had didn't affect me.
I don't know the answer, but I'm going to guess that it's because they want to build or rebuild their credit, and would not be eligible for credit cards otherwise, even at a rate of 28% with unsecured credit. For example, maybe they have recently become bankrupt, or their credit score is really bad, or they have no credit history, so the only way they can get a credit card is with a secured card. This would allow them to build positive credit history in a way that paying with cash or a debit card would not.
