The deeming of a failure on a passive alcohol sensor, with which the officer can then demand a sample on an approved screening device, could be said to be another tool the officer can use, to the extent that it prevents people from going out and drinking and driving, because they can be more easily detected. For example, if the officer has a cold, they would not be detected. This way, they would be detected through the passive sensor.
It has been expressed earlier, and others have expressed it this way, that a passive alcohol sensor is an extension of the officer's nose.