Maybe you shouldn't look for logic. Cause even if they keep it there can two dogs with the same title while one would beat the shit out the other.

Why 3 wins, why not 4, to make Champion? Why 5 wins, why not 6, to make Grand Champion?, etc.
Maybe the harder to make a champion or grand champion the more people would agree they deserve to keep the title? You cannot judge any dog's wins individual so it has to be by numbers. Might encourage people to continue too if they were to keep the title.