The closest we have is the indication that Gold values nature and survival of the fittest. They assume that the natural state is superior to the Carved, and probably would not respect results that they knew were from Carving. The Board of Quality Control expects and enforces this:
"...Except for the Obsidians, only we wait nine months to be born.
Our mothers receive no catalysts, no sedatives, no nucleics. Have you
asked yourself why?"
"So the product can be pure."
"And so that nature is given a chance to kill us. The Board of
Quality Control is firmly convinced that 13.6213 percent of all Gold
children should die before one year of age. Sometimes they make
reality fit this number." He splays out his thin hands. "Why?
Because they believe civilization weakens natural selection..."
Despite what we see with Mickey and Darrow, it is not assumed that Carving is superior to the natural product:
"The golden ancestors. They call them the iron Golds.... What
creatures they were." [Mickey's] eyes go distant. "It took
generations of eugenics and biological tampering to make them. Forced
Darwinism."
He's quiet for a moment, and then it seems an anger builds in him.
"They say Carvers will never duplicate the beauty of the Golden Man.
The Board of Quality Control taunts us."
Fitchner clearly shows how poorly Gold thinks of Carving:
"You are ugly and you eat like a pig, Fitchner, but you chew
metabolizers when you could just go to a Carver and fix yourself to
look like the others. They could take care of that paunch in a
second."
Fitchner's jaw muscle flickers. Is it anger?
"Why should I have to visit a Carver?" he hisses suddenly. "I can
kill an Obsidian with my bare hands. An Obsidian.... Why should I make
myself look any different?"
"Because it holds you back."
"Despite my low birth, I am of note. I am important." His hatchet
face dares me to contradict. "I am Gold. I am a king of man. I do
not change to suit others."
The most thorough example comes from Mustang talking about her Mother, and her Father's choices:
..."When I was six, my mother was pregnant with a little girl. The
doctor said that there would be complications with the birth and
recommended intervening medically. But my father said that if the
child was not fit to survive birth, it did not deserve life. We can
fly between the stars. Mold the planets, but my father let my sister
die in my mother's womb.
"The hell?" Holiday mutters. "Why not give her cell therapy? You got
the money."
"Purity in the product," Mustang says.
As for why Gold's wouldn't do this, given the other cheating that we see go on... In-universe, the Board of Quality Control would probably be the roadblock. Just as they check for cheating, if they felt Carving was a realistic threat to Gold "purity", they'd be testing for that as well. (The fact that Darrow's carving was so spectacularly successful surprises everyone; it's implied in a few places that Carving is viewed as a toy rather than a tool - as cosmetic surgery).
Out-of-universe, there are many aspects of the culling and selection of peerless scarred that are ludicrous on the face of it. It starts with a 50% death rate, with no warning given to the entrants? What are the chances that something in society would have a 50%+ mortality rate and it never gets talked about where future entrants might hear about it? It takes in a class that is half exceptional and half fodder and nobody raises concerns that it's a cattle drive? It's a secret, but aspects of Darrow's victory are public knowledge? It's not the most coherent part of the books.
Quotes are from Red Rising chapter 20, Red Rising chapter 12, Red Rising chapter 29, and Morning Star chapter 28. All bolded text is my emphasis.
