There's a massive market out there for the world of bad credit. Think about all the entitlement types living off the gov't dole, plus the criminals that can't get regular work...the mentally unstable that can't hold jobs...substance abusers...the list goes on.
At 30% interest on a 20K car loan for an 8 year term (remember they can't get anything anywhere else), that's 12K in interest if you can keep them making payments for just 2 years - and they still owe 18K in principal. With today's technology, you often wind up repo'ing the car anyway. Even with huge default rates...this is big money for those that can stomach it.
A few decades ago, I used to repo cars for these guys.