Hip X-rays and other health tests are not really necessary for the normal, everyday pet.

They might be helpful if you plan on doing a lot of walking, jumping or even doing agility.

But normally these tests are only performed on dogs who are going to be bred. Because many of these health problems can be genetic, breeders don't want dogs to pass the bad gene onto their puppies. So, any dog that does not pass the health tests, will be spayed in an effort to eliminate these health problems altogether.