The theory goes: Poor people who need a car should buy a modest car, and keep it running for as long as they possibly can. But some poor people don't do this. They buy an expensive car using weird debt structures that they don't understand, and then when a minor thing goes wrong (traffic ticket for example) they get trapped in a cycle of debt.

I think this probably does happen, but I'd be interested to know how many people are stuck in debt because they bought a product using a financial product they didn't understand vs it just happened.

This thread has a bunch of stuff about these potentially mis-sold financial products: https://news.ycombinator.com/item?id=14476381