Why does Chett survive the prologue but the other prologue POV characters do not?

Question

In this answer the OP says the following (emphasis mine).

Pate is the viewpoint character and while his death is not explicitly confirmed (he might have just fainted from his wounds), the viewpoint character of all other book prologues has died, so we can assume that Pate did too.

I'd never made this connection before and so looked into it, we have:

• A Game of Thrones: Will is killed by the wight of Ser Waymar Royce
• A Clash of Kings: Maester Cressen drinks poison and dies
• A Storm of Swords: Chett is killed in the battle with the Others
• A Feast for Crows: Pate is poisoned
• A Dance with Dragons: Varamyr Sixskins succumbs to his wounds

The odd one out here is Chett as all the other characters die in the prologue, while his ends with him and Sam hearing the three horn blasts.

Samwell Tarly stood shaking, his face the same color as the snow that swirled down all around them. "Three," he squeaked to Chett, "that was three, I heard three. They never blow three. Not for hundreds and thousands of years. Three means—"
"—Others." Chett made a sound that was half a laugh and half a sob, and suddenly his smallclothes were wet, and he could feel the piss running down his leg, see steam rising off the front of his breeches.
_{A Storm of Swords, Prologue}

Is there any reason why Chett survives the prologue and not the others? Has George R. R. Martin commented on this before?

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I am looking for an out of universe answer on the meanings of why this is the case.

Answer 1

Because George R.R. Martin likes to keep his readers on their toes.

Martin also addresses his Comic-Con panel reveal that the character of Jeyne Westerling — who Robb Stark marries in the novels and is still alive, unlike her show counterpart Talisa — will appear in “The Winds of Winter” prologue. But that doesn’t necessarily mean that she will die, or that this will be the last fans see of her.
“Let me make this clear here: I didn’t say she was the viewpoint character. I said she was in the prologue. It’s the viewpoint character who always dies,” he says. “I like to break rules. Just when I get it established what the rule is, I like to break it. So maybe the viewpoint character will die in the prologue, and maybe they won’t.”

_{—George R.R. Martin in an interview with Zap2it after the San Diego Comic-Con 2014 "Game of Thrones" panel (emphasis added).}

Answer 2

The facts are:

1. We almost never see the actual death of POV character. We see the few moments to few minutes before death, but not the POV of death. Out of all the POV characters you mentioned, the only people who we see die are Will, Cressen and Varamyr. And even while Cressen knew he was dying, we don't get "And then he lost consciousness and was dead." line. Varamyr watches from his other body. With Will, we see up until the point of the wight starting to choke him to death. Pate knew he was losing consciousness and that something was odd, but he didn't know he was dying. For all we know, Cressen and Pate could have fallen into a deep coma and died days later. So, the question by itself doesn't make sense: none of the characters actually die in their prologue chapter, although it is implied in all cases that their death is certain. Varamyr is special case, because he got true death of a human but has moved into the wolf.

2. It's the start of the battle. GRRM didn't want to show us the details, scene by scene recording just yet. Chett did die later, though, just a few minutes after the prologue. The author gave us the opportunity to care for the character, rapist and murderer that he was, and hope he had survived, only to dash that hope in a later chapter. The prologue served its purpose: made us care for the character, learn more about the world, learn new info which other characters do not know, make the world "wider", as if it doesn't revolve around main characters.