Lets say you race and beat a guy in a Camaro, but only by a couple tenths in the 1/4, and you had to spray to do it. It sucks to know, that once that bottle is empty, the guy in the other lane would own your ass every time. With a supercharger or turbo, you get to play all day long, knowing that your car isn't relying on the contents of a 10lb container to be fast. Once that bottle is dry, you have to tuck your tail between your legs and go home.
I'm not saying that nitrous cars aren't fun or cool, but IMHO, a force-fed car is much more impressive than a bottle-fed car.