Part of advertising spin about why we need to feed our dogs commercially made pet food is because it is 'balanced and complete' and most vets will say (rightly) that dogs have different needs to humans and you can't be sure that food you make will be 'balanced and complete'.
Stepping back a bit, this concept comes from AAFCO (and other erstwhile bodies), the acronym stands for American Association of Feed Control Officials, the body that sets the standards for all livestock.
The first problem comes in that we no longer think of dogs as 'livestock'.
Livestock feeding is price sensitive, you want to grow the animal fast enough and as cheaply as possible to get it to market (that is – turn it into food that we eat).
Food as we think of it is not the way that a manufacturer thinks about it.
Calories, that is energy (which is what a calorie is) is separated from what the body needs as the elements to sustain life and grow. It is easier to find calories and add the synthetic elements, amino acids, the vitamins and minerals that we normally think of in food, as separate components, to be added as required. So the 'food' is made in a lab, and this is one part of the 'complete' equation. That is, all the amino acids, the vitamins and minerals are synthetically added into the product, and over time they have learnt how much of these are required.
In the beginning of course there were short cuts, inadequate amounts of macro and micronutrients being included and some ingredients (albeit synthetic) are more expensive than others, so marketers were quick to pick up on promoting their Petfood product as 'balanced and complete' compared to the other 'cheaper' brands.
So what starts out as a way to be superior to other lesser brands becomes the industry norm over time, and is now the reasoning behind why we can't feed our dogs ourselves.
And yes, Dogs do have different needs, and these blogs will over time talk about these.
Thank you for sharing the journey.