Drug dogs are covers for lies. Here's how -
1. Cops ask to search cars for no reason at all. Most Americans are too meek to say "no" because government schools have conditioned them to submit to government and have taught them nothing about their rights. When drivers say "no," then some cops tell drivers that further action is inevitable because radio dispatch "has a drug dog on the way over." It is often a lie to induce consent. There is no dog on the way.
2. If a dog is or is not "on the way," cops add additional lies to make drivers think that there will be a long wait and that the driver must stay until a dog arrives. Cops rely on driver ignorance of the fact that evidence will be suppressed if drivers are detained longer than it takes to complete the traffic stop (e.g. write the ticket). Drivers are induced to consent to search to avoid a long wait based on lies.
3. If a dog is enroute, cops let drivers think that they are obliged to stay even when the cop has no reason to detain drivers any longer. The cop's rationalization is that drivers loiter roadside with cops for no apparent reason or because drivers enjoy waiting for dog sniffs. Cops take advantage of drivers who are too stupid (or too meek) to ask if they are free to go, so that drivers "consent" to unwarranted detention by not leaving.