Car Surfing

I got introduced to this term recently as I had to take care of a car surfer with bruised brain. This life thretening activity is usually done by teenagers who have lots of muscles and not much of brains. They will climb out the window while he car is moving and into the roof and will do their surfing thing. Usually they end in the Emergency room or in the ICU or even 6 feet under.
What's wrong with playing a real sport, watching a movie or god forbids reading a book?