I'm very new so if there are formal written standards from CGC about grading I don't know about them. I would imagine it would be almost impossible to write down EVERY single possible reason for giving a comic a particular grade. Given that damage to a book can occur an infinite number of ways how could you account for every possible defect? One book has a blunt corner and everything else is perfect, another has a semi circle ding where someone placed a coffee mug on it, another has a crease, the list would never end. So the CGC method of letting multiple graders give unique blind opinions seems to be the most honest way to conduct an otherwise "imperfect" process. But again, my point ultimately is that CGC is in my opinion providing a service that is needed, and seems to be well received and valued by other collectors. How do I know? Because CGC books sell for more than other graded books, indicating buyers seem to trust their opinions, and better yet they trust when they go to sell their book they can have a better idea what they expect to get for the book.
The very cash we spend every single day is just paper, but we accept its value because we know we can use it to buy stuff, we know stores will take the money. If I have a CGC book I know what it is worth because I can easily check the going price for it. If you feel that CGC grades unfairly, is crooked, manipulating the system etc then you dont accept their standards either written or unwritten, you dont accept that value, then thats your choice and you can go along collecting any way you like.
I stand by my statement that CGC is the yardstick by which to grade / compare comic book condition relative to the market as a whole.