We do not understand the complexity and importance of the food. But one thing is known by those who seek the truth; and it is species-specific diet is very important for the health of everyone, including your pet. You can also look at the best animal charity organization in San Diego.
Maximum persons with pets rely on commercial pet food, with little thought of how nutritious as possible. This is understandable when you realize that most people do not feed themselves with nutritious foods, instead of relying on junk food, fast food, restaurant food, anything other than real food.
The fact is, food is very important for health. If you or your pet, do not eat nutritious (ie quality), species-specific (ie that which your ancestors evolved to) food, then do not imagine either you or your pet, be healthy. It's really very simple.
However, the man wanted to make something more complicated than it really is. That is human beings with interests vested.
Only a few decades ago, it was common to feed the rest of the pet from the table. This was in the days when the family diet is healthier than now and when the agricultural growing real food, rather than chemical-laden 'food' produced today.
And, for the most part, pets thrive. This is not an unreasonable diet for dogs and cats are best equipped with their diet with a little hunting.