It is, for example, much more likely that the BG who is scouting you will decide to go to a house without a dog than that he will come up with an elaborate plan to silently kill your dog. BGs aren't looking for a challenge, they are looking to enrich themselves with the least effort possible.
That's true with one or two bad guys. But if 5 bad guys have scouted your house, know you have a dog, and decide to come in anyway, they probably have made arrangements for dealing with it. A baseball bat to the head doesn't make a whole lot of noise.