
It is the main reason most people show, so their dogs can be compared to the breed standard by judges and the results over a season (as obviously judges opinions will vary slightly) give you a fair idea of how your dogs compares to the competition based on results achieved.
You also have to take into account development, as pups can go through some awful stages, and then at the other end some dogs mature well and can continue to look the part for years and others go over, or age (loose fitness and shape etc) quickly.