Obviously, I must be wrong but what am I missing?
Your not missing anything on the construction side of things, energy absorption in design is well founded and used by several racing organizations in their rule packages, as are penetration barriers for racing environments that might expose the driver to "spearing".
F1 and Indy racing league require Zylon anti penetration and energy absorption panels in the chassis construction of the drivers safety cell.
Both nose cone and rear crush structures are also mandated to absorb energy on impact when the car noses into or backs into the wall. In older designs the rear trans-axle formed a very rigid structure that causes huge deceleration loads if the car backed into the wall at speed. Now they have a little crush structure that is bolted on the rear of the trans-axle to dissipate energy on such an impact.
http://www.formula1-dictionary.net/nose_cone.htmlThe New generation NASCAR cars have foam inserts, and a penetration barrier steel panel in the doors to absorb crash energy, and distribute loads.
http://stockcarscience.com/scienceTopics/scsCarSafety_IMPAXX.phpEnergy absorption is often the only way to make protective structures survive major critical impacts.
Even radioactive materials casks include energy absorption structures so they can physically survive catastrophic impacts.
It is a very well demonstrated concept and rules packages should not make it impossible for the builder to design crush and energy absorption into the design. Unfortunately well meaning regulations that require roll structures placed as close as practical to the exterior body panels do in effect make it impossible to design into the structure planned crush and energy absorption.
Larry