When kept outdoors, the car is left at the mercy of nature, which, to be frank, is not very merciful at all. The rain, snow, sun, wind, etc, all of them have diverse effects on the exteriors as well as interiors of cars.
To begin with, the rain leaves ugly water-marks, and causes the body-work to rust with time. The acid in the rain eats away at the paint-work, and makes it very patchy. The snow freezes over the car, including the brakes. This is extremely dangerous as it prevents the brakes from working efficiently enough, and could be fatal.
If a car is left in the sun, the interior over-heats. This damages the internal workings, as well as making it rather unbearably stuffy to drive in. As for the exterior, the paint-work and finish gets bleached and worn away due to the ultra-violet rays from the sun. The car will end up looking much older than it really is.
Wind-storms bring up with them anything that has been left lying in the streets, such as sticks and stones. When these are made to fly through the air in the wind, they scratch and dent cars along the way.
Birds muck and tree sap are two nuisances a car will be stained with when it is parked outdoors. These stains look most unsightly, and they are extremely hard to get rid of.
It doesn’t make a difference if the car is parked indoors or outdoors, either way, the car get dusty. Dust gathers anywhere and makes the car look old and worn out.
When the car is parked indoors, it is still not safe from scratches and dents. As the garbage is being taken out, it will often bang and knock the car. If the bag contains something a bit heavier this can leave a permanent impression on the exterior. Also, garages are usually not the most spacious, and when people squeeze past the car the can scratch it if they have things hanging from their pockets or belts. These little accidents are seemingly nothing, nonetheless they leave visible marks.
A car cover will prevent all of the above from wrecking the car. All-weather covers are waterproof and ultra-violet resistant and will protect any car from the sun, rain, and snow. The cover itself will be able to absorb the shock of knocks and bangs and prevent the car from getting dented and scratched.
There are covers specifically designed for the indoors. These too will be able to prevent a car from getting scratched and dented, and are also dust-proof. The are water and uv resistant, though on a much lower scale to outdoor covers. This is so that owner can benefit from an occasional outdoor use too.