You could, although with the car higher off the ground, it allows better air flow underneath for moisture control and fewer incentives for a mouse to climb in. Plus cleaning along the lower sides of the car is easier laying on the cardboard when elevated and it's cheap, because we get cardboard packages here all the time. If it gets musty or damp, throw it out and replace it. I'm guessing rug fibers might attract unwanted pests more and it would not be as easy to vacuum there. My unheated attached garage may generate more moisture with the WNY climate here than yours, and I won't need to pull out a damp rug (especially one with the car parked on it). Never had flat spots on the 40psi inflated tires either. Finally, since the cardboard is under the cars and not seen, it doesn't look bad. if you want, throw those perfumed type dryer sheets under it for more pest control. I admit putting cardboard under a $70,000 car sounds dorky, but it works.