Yes it certainly can.  A thief wants to get into your vehicle, start it,
 and drive off as quickly as possible.  As soon as a thief starts to 
make an entry, they are exposed.  A car cover takes a few minutes to 
remove, so the thief's exposure time is increased.  With so many cars 
uncovered, why would a thief want to increase the risk of being caught? 
 A cover also helps protect the contents of a vehicle.  When radios and 
other items are out of sight they are less likely to tempt a thief.To stop the car cover being stolen - Paint your name on the front of the car cover