
Hi guest - you've raised some interesting questions! The first thing to bear in mind is that all dogs have faults - there is not one single 'perfect example' of any breed anywhere in the world. But that is what responsible breeders are striving to attain. Genetics, however, is a very complex subject, and just because both parents are fantastic there is no guarantee that there offspring will take after them in all respects.
Showing the dogs is about the best way to get an objective view of how good quality a dog is. If it is consistently placed by different judges, then it may well be worth breeding from. If it is almost never placed, then really it's an 'also-ran'. What an animal like this may still have to offer the future of the breed, though, is excellent health. If it passes its relevant breed health tests supremely well it may still be worth breeding from, but you would have to be even more selective in the choice of mate.
The sort of animal that should never be considered for breeding is one who has been unsuccessfully shown and whose health checks have been unsatisfactory.
Hope this helps a bit.
:)