>>I can see it now. One of Dragan's questions will be, "Why do they climb in and out of the windows?"
>
>Being a Southerner for over a decade you would think that I should know this, but why do they? Speed? Car stability? It looks cool?
>
>Renoir

The bodies are sheet metal. Having a door would require additional framework, not to mention the work to recreate one. Further, the frame of the car is tubular steel that's runs across the area where the door would be. Placing a door there would compromise the structural integrity of the car's side.