Seems like the more I learn about the system the more of a scam it seems.
Speaking of which Serial season 3 just started which covers this kind of stuff, more in the small than a grand ‘Thing X is the problem we want solved that will make things much better’.
I have been assuming that dogs give false positives every now and then, and there's a search for some actual evidence based on that indication, which everyone knows can be a false positive.
Every time this technique leads to a search that is used to secure a conviction, it erodes your rights, as a non-criminal, against arbitrary search and seizure.
(Same applies for e.g. DUI testing on the roads; the police has the right to take alcohol test of any driver, without anyone looking like they're driving badly.)
Any arbitrary seizure, if only based on dog indication, is of course a horrible miscarriage of justice.
DUI testing is different. In many jurisdictions you do not have to submit to it, if you are fine with losing your driving privileges - which is not a criminal penalty.
I'm not super pleased about it, but there is typically a clear line - some voluntary behavior voids your liberties. Involuntary behavior generally should not.
So you're a cop and you want to search someone, but don't have the legal basis to do so? Go get the dog and get him excited.