Wow, that's a "thinker" question.
First, I think a lot of it has to do with the chain that flows from manufacturers to retailers (in the auto industry aspect of your question). Most car dealers buy their goods from suppliers on credit, don't they? They don't pay for the new car outright in order to sell it at a profit. If the consumer buys the car on credit, the debt load then gets passed to the financier, who passes it on to the car buyer. It's like the debt load just trickles downhill. If the consumer paid cash or made a very large down payment, that debt is smaller and can't trickle so far. But I am not a financial expert, so I'm sure the nuances to the flow are much more detailed than that!
The housing market is different, I think, at least for existing houses and not new construction. That is WAY over my head, and I'd love to hear more about that from someone in the business.
I think a lot of the recession comes down to one simple word, "GREED." If banks hadn't been so greedy for a potential profit and given loans to every Tom, Dick, and Harry without a thorough background check, they would be a lot more stable. And now we are in hot water with the world economy, because many banks have packaged up this bad debt to look so pretty, and other countries bought our debt (the debt load trickles farther). Yet that debt load must stop somewhere, and no one wants to pay for it.
The greed also falls onto the average consumer. We want to keep up with our neighbors who bought a brand spankin-new SUV, and we want to look as good as they do. So we buy the car we can't afford. Our neighbors' kids are going to private school--we don't want to look like we don't love our kids, so we send them to expensive schools, too--schools we can't afford. Our kids' friends just got the biggest iPod/toy/electronic gadget on the market, and our kids beg us to give them one just like it. Instead of waiting until the price comes down, we give in and buy it for them so our kids can be cool and hip as well.