Most people that produce band dog that I'm aware of are trying to create a large superior dog. They believe they can get the best traits from more than one breed to create their ultimate dog.  Unfortunately genetics don't work quite like that. This is why golden doodles, puggles, etc aren't breeds yet. They can't produce consistency that is required for it to be it's own breed with a standard.  It takes  many generations of breedings to accomplish this. The same can be said for backyard breeders that don't understand genetics. They will breed a small dog with a big dog hoping to balance out the pups.  They'll breed a dog with a bad rear end with a dog with a good rear expecting balance and believing they have achieved it. Genes, genotype do not work that way. It is much more scientific.  Dogs have dominant and recessive traits. The more dominant trait they have alike the greater the likelihood the litter will have those same traits. There is a mathematical equation that will predict the percentage of the likelihood.  Recessive traits will show up too. There is a lot of research out there on this.