What's the difference between a loan shark and a Discover Card?

Yeah, it's not that funny a joke because as I'm reading this Discover Card application that my wife received, I realized that the answer was "not very much." In fact, I'm pretty amazed that it's even legal for Discover to do this: their default rate on "The Miles Card from Discover" is a reasonable 13.99%. Not great, but not outrageous.

But you read the small print - as usual - and a very different story emerges: if you are late making any payment, the default introductory APR rate jumps to 19.99%, and then if you're late a total of three times, your interest rate jumps to a staggering 24.99%. That's really astonishing and that's why I suggest that there isn't much difference between this deal from Discover Cards and the local loan shark. I mean, 25%? Do people sign up for this kind of miserable deal?