It's likely due to the way the deal works between the car companies and PD. The interior seen when in the shop is likely a basic, low poly version that doesn't have movement options for the shifter(s) or the steering wheel. It's likely only there to prevent you from seeing through the car (as devs obviously don't put textures on sides of objects you're not supposed to see), and nothing more. Also, Jay Leno didn't drive it, though I know what you're talking about. The 'real' version of the car isn't completely functional or road legal.