Passage Two

Taiwan police cannot decide whether to treat it as an extremely clever act of stealing or an even cleverer cheat (诈骗). Either way, it could be the perfect crime (犯罪), because the criminals are birds—homing pigeons! The crime begins with a telephone message to the owner of a stolen car. if you want the car back, pay up then. The car owner is directed to a park, told where to find a bird cage and how to attach money to the neck of the pigeon inside. Carrying the money in a tiny bag, the pigeon flies off. There have been at least four such pigeon pick-ups in Changwa. What at first seemed like the work of a clever stay at-home car thief, however, may in fact be the work of an even lazier and more inventive criminal mind one that avoids (避免) not only collecting money but going out to steal the car in the first place. Police officer Chen says that the criminal probably has played a double trick, he gets money for things he cannot possibly return. Instead of stealing cars, he lets someone else do it and then waits for the car-owner to place an ad (启示) in the newspaper asking for help. The theory is supported by the fact that, so far, none of the stolen cars have been returned. Also, the amount of money demanded—under 3,000 Taiwanese dollars—seems too little for a car worth many times more. Demands for pigeon-delivered money stopped as soon as the press reported the story. And even if they start again, Chen holds little hope of catching the criminal. "We have more important things to do," he said.

The writer mentions the fact that "none of the stolen cars have been returned" to show ______.