There are altered classes offered at some shows and in the veterans class, they don't have to be intact.

There is so much that goes into breeding dogs and what makes a good stud dog. A dog may cross wonderful on certain lines, or certain bitches and horribly on others. You really have to look closer at pedigrees than you do in horses.

There is just no point in showing altered dogs. It isn't like showing stallions, which are usually(not always) a serious PITA to deal with and have to have a different life than if they are a gelding. It just isn't a big deal to leave a dog intact. You don't HAVE to breed it just because it has testicles. Same with bitches.