When cars get into a collision, why does it seem like half the car gets turned into debris?
The answer is simple, conservation of momentum.
In elastic collisions, like car crashes, the projectiles have a lot of momentum. If a head on collision occurred where the cars stayed perfectly rigid, the occupants would have a huge change in momentum. This used to happen before modern safety regulations. Modern cars are designed to "give", absorbing a large amount of momentum and keeping the occupants from experiencing the same change in momentum, saving lives and livelihoods in the process.
It is a lot better to lose more of your car than losing more of your body.