In case you were wondering why modern race cars are required to have such overbuilt roll cages, this video is a good reminder. It's footage of a brutal rally crash that leaves an Opel Astra completely destroyed—save for the section protected by the cage.
This wreck happened on the second stage of last weekend in Finland. Driver Kari Kallio and co-driver Markus Oksanen came into a downhill right-hander when their Opel Astra hatchback oversteered mid-corner. Kallio overcorrected, and couldn't stop from getting sucked into the ditch on the outside. The car rolled multiple times before finally coming to a stop right-side up.
As you can see from the picture above, the car was completely destroyed. The back half of the cabin was totally caved in, but the front half—where the roll cage is—held up, saving Kallio and Oksanen from serious injury. Note the creased corner in the roof where the roll cage starts. They were even able to open the door and exit without issue.
This just goes to show you should never cheap out on safety equipment. It could save your life.