A car cover may seem like a genius idea - it will keep dirt, dust, and spills off your car!
However, there are actually more cons than pros.
Firstly, having dirt and dust on your car in and of itself is not damaging to your paint. The way you decide to remove it will dictate if the paint becomes scratched or not.
Secondly, at least 99% of car covers are very generic and not soft or form fitting to your specific vehicle. This means that it will be flapping around in the wind and rubbing against your paint, causing swirls and scratches.
Lastly, once a car cover actually does its job and collects dirt and debris, it is very difficult to remove the cover without getting that debris back onto the car. Most people are not cleaning their cover after each use either - this leads to scratching the paint every time the cover is taken off and put back on the vehicle.
So is there ever a use for a car cover?
Yes, but only in rare circumstances.
One time uses, such as work/construction being done around your house or neighborhood and then cleaning the car cover professionally (dry cleaning) afterwards would be acceptable.
When these circumstances arise, then your car cover will be clean and ready for the next potential use.