Connecting the dots...   

   As a child growing up in the 1940s and -50s, I remember my grandmother feeding their dog real food as she prepared the family meal.  Granted, she fed meat and veggie scraps, but it was real food--mostly raw.
    While seemingly unrelated, I also recall TV shows and press articles predicting that, within a few decades, scientists will develop a food pill or food pellet and people will no longer have to eat fresh real food1.  A major concern at the time was how to add 'bulk' to keep our digestive tract functioning properly.  Scientists determined that food pellets containing bulking material were an alternative to a pill.
    And at about the same time, agribusinesses that were processing food for human consumption, needed a way to dispose of animal and plant processing by-products.  They realized that they could dispose of this material and make a profit by selling it as dog food to feed the growing dog population.  Bingo!  A new and profitable business model was born.
    In the 1940s,  Kibble was only beginning to be advertised on the radio and in newspapers.  TV advertising began in the 1950s2 and was promoted as being "...everything your dog will ever need."  Gullible us, we believed it.

    The lesson here is:  Kibble, a manufactured food-like substance, is intended to pass for real food for your dog.  It is not the food your dog evolved to eat.  It is what agribusiness and many veterinarians want you to believe is healthier and more nutritious than real food.  Surely you can think this through for yourself and see the absurdity.

1 = Search Google's Ngram Viewer for early mention of food pill and/or pellet.
2 = Search You Tube for "1950 dog food commercial"