>I just personally still don't understand fully how KC registering stops any fowl play?
I can put it in these terms, Josh... I used to breed & show pedigree cats. During that time I took an interest in tracing pedigrees back to the original imports of my (very old) breed. At that time, nobody else had done it.
Together with another breeder, we wrote to many people in the UK and overseas and got pedigrees sent back to us, often with letters about the individual cats and photos too. It was before the internet, and the pleasure we got from making contact and finding out stuff about the ancestors of our cats was wonderful as well as educational and sometimes helpful from a genetics viewpoint. This was only possible because all the cats were registered, going back to the 1800's.... My work back then has now become part of a global database, and yes, health issues are able to be traced if needed. I even travelled halfway around the world, twice, to gather new information about the breed's genesis.
My dog's a crossbreed.... a first- cross between two breeds, but his father I knew was KC reg. I had very few some details, but I asked someone knowledgeable in his father's breed and within a few days I was given a name and links to that side of his family. I know now that his father tested clear of hip and eye issues and epilepsy, and so did his ancestors. I have even found photos online of that side of the family, and I can go back many generations... because of an internet database just like that I helped create with the cats!

Don't know anything at all about his mother's side as she was farm bred and that's where the story stops. If he has bad eyes and/or hips then I know where they DIDN'T come from. Registration is so much more than a silly bit of paper, it is access to hundreds of years of data and ancestry, and history.
Acquiring a dog may be the only opportunity a human ever has to choose a relative.