Having a dog with you and making it clear that the dog rides shotgun always, gets cops to know what your justifiable defense will be. Also the grounds for the cash wealthy drop dead easy lawsuit. 
Many Judges (criminal and civil) are very skeptical on what it is that a dog 'marks' on. Are they excited about drugs, or the smell of another dog, or the melted chocolate in the seat. They're calling attention to something, which the handler interprets. Judges are having a fair amount of doubt on the interpretations of what a dog thinks (by anyone). Like bringing a crime witching stick.

Dogs are a threat. Brought to searches to instill fear. That's what just happened in Longmont. warrentless searches with dogs. Its all about fear.