Why do some breeders require a contract?

If you are purchasing a puppy from a reputable breeder, they will require a contract for a few reasons. It will outline what they offer as part of the purchase agreement. What it also outlines is the breeders expectation of you as the purchaser.

Reputable breeder will give you clear expectations of what they expect from you. For example, my own contract makes it clear that all of my pups are to be raised indoors, the buyer agrees that the puppy is being purchased as a companion animal and agree to regular vet care. I also require all of my pups to be spayed/neutered by a certain age.

There is more in there but this gives you an idea.