"Only works until it doesn't" can be said about literally every single mechanism made by man!
It's a statistics game. you can't reduce the chance of theft to 0.0% but you can work on getting it as close as physically possible whilst still maintaining some level of utility.
Thieves are opportunistic, sure, but they are also predators by nature and are looking for a likely target...
There was a joke we used to make when I grew up in Africa as a kid... You don't need to be the fastest kid in the world to escape the lion, only faster than at least one of your mates. The idea was that we would always be giving gives sweets and crisps to Rob so that he'd end up lardier than the rest of us.
A thief is going to be scouting out which car is the most likely to contain the bacon. Since he can't break into every car, he will go for the one he perceives to have the highest chance of a solid catch.
By making your car less appealing you are adding an extra level of security right there. Very few security measures are used solo. most are stacked with something else.