Which is why we have breed standards - they are a guideline for breeders to breed to, so that people who want a particular breed should be able to know roughly what they will look like and what size they will be - but if the breeder has not bred from correct size dogs then who knows what the puppies will be like. Just say for example you breed your big Westie with another big Westie and you end up with very big puppies, then in a short while the dogs will end up much bigger than what people expect Westies to be like. Unfortunately if people are only breeding for money then they do not care what dog they use on what bitch, only that they can put a male and female together and get puppies to sell! When I breed a litter I study pedigrees going back ten or more generations, so that I know whether the mating will be compatible and whether they will turn out how I want them to in terms of breed type, temperament, size, colour, etc.