If you could see what your cars are made of, people, you'd shoot yourselves.

The roof is two sheets of metal cushioned by corrugated cardboard.

The bumper is a big piece of plastic about the thickness of a Tupperware lid.

Behind the bumper, there is a dense wad of Styrofoam.

Your air bags have to be shipped by ground mail because the gun powder like substance that ignites it at the point of impact is considered, by the postal service, to be no different from a bomb.

Your rear view mirror is held on by a $2 bottle of glue when you bought your car. It will eventually fall off.

The most expensive pieces of your car, by size ratio, are the plastic moldings on the sides of your door to prevent too many door dings.

Almost all the sheet metal on your car has the thickness of the side of a toaster.

The top of your doors' frame can be bent back like tin foil if someone really wants to break into your car.

(For my area) The cars mostly stolen for a joy ride are Mustangs and Minivans (don't ask, I don't know either), while the ones never recovered are Nissan Altimas, Honda Civics, and Toyota Camrys. Their ignition cylinders break like candy.

You often don't even know where your fusebox is.

You seldom ever raise your hood to see why you have no windshield wiper fluid. Where do you think that neat blue stuff comes from, genius?

You really need to clean out your trunk once in a while, especially if it's expecting our company.

By the way, do you ever clean out this hunk of junk?

Welding a part onto your car means we cut the old one off, like with Frankenstein.

Most of your car is made pieces of plastic that are always more expensive than they're ever worth, and come in a bazillion different shades of gray.

Yeah, well, there's a really good reason that cars are made of that stuff. Don't be scared about what little your car is made of; chances are, it's trying to protect you (the driver and passenger) from harm when there is a crash.

When you look at a car crash on the news - particularly a front-on one - you'd think "Fuck, me." You should think "The newsreader's a dipshit. He's not 'lucky to be alive'. He's alive because of the awesomely awesome design of that car." Indeed, cars are designed to be tough, but soft. Reason? It involves a little physics. Take a seat. Have a marshmallow. Let me explain.

In physics terms, they're designed to have a large crumple zone so that the stopping force is spread out over as much time as possible, causing minimal damage to the occupants (although making for a really rotten-looking car afterwards). In non-physics terms, it's the same as jumping out of a tree or off a roof. If you land while bending your knees, it doesn't hurt as much as if you'd landed with your legs straight. You've probably also done some damage to those there legs.

This can also be explained in terms of George Of The Jungle. He hits so many trees that he should probably be dead by now, becase he has a huge stopping force all in one micro-second. If he hit rubber trees, he's be slightly safer as the rubber would provide the same stopping force over a longer period of time.
Even if you're skiing (which was the analogy I learned when I learned about stopping forces), one can slow down with minimal harm if one simply sits down and stops the skis touching the snow. However, one gets more than a sharp pain if one follow's George's idea of crashing into a tree.

So having your car made of those light, inexpensive, easily broken materials means that not only are production costs lowered, but you, the driver, are a lot safer than if it were rock solid.