The same reasons that millions and millions of enthusiasts do every year with every car on the planet. 1) Differentiation from other owners of the same car. 2) Fun 3) Better performance or gas mileage.

 

I need to just let my wife drive. She averages about 28mpg... I get 25mpg.... driving styles have alot to do with MPG with our 400H....I guess I am a bit more aggressive

 

I've put about 2000 miles on mine now, and I'm getting 25mpg (combined) on every tank. Not that bad. I have to drive VERY conservatively to get that though. If I drive totally normally, it's more like 23.0-23.5.