from what i hear the ausies use holders because legally they are only spose to have two dogs on a hog at a time, not for sure, just what i have heard. I personally like the holding dogs, and real gritty bay dogs.
im a aussie and we use holders cause "well what i think" its the best way to hunt and alot of people over here hunt with about 4 dogs we can have as many as we want but i just hunt with one dog or sometimes two cause i think one out hunting is the best lol