The obvious joke is they don't get stolen because nobody wants them.
Let's assume the motive is profit and dig a little deeper.
First there has to be a demand either for the entire car or the parts.
Given time anything can be stolen. It takes time to a remove an airbag or catalytic converter. It also requires some knowledge.
One would think the demand would be for the battery or air bag.
Cameras don't seem to be that much of a deterrent. Consider "porch pirates."
Demand and expertise may increase.
Let's hope the numbers stay low.