
In short, yes it does matter if you show them. Breeders who are interested in improving the breed and producing typical high quality pups will want to use the best available Stud dogs to their bitches. They will only be able to do this if they can see what the dog is like, how he stacks up against others, and how his pups turn out (so this means showing).
Unfortunately there are plenty of Westies, KC registered and not that have been bred with no consideration for the breed standard, health or temperament, and a lot of them bare little resemblance to a typical WHW, other than being white.
Your dogs may be super examples, or they may just be nice little dogs with little quality. Unless you have experience in evaluting the good and bad points of a dog against the breed standard, your are unlikely to know which they are.