Why is watching your wife being fucked by another man so different from watching some other couple having sex?
In The Beginning Was The Word
As Humpty Dumpty said to Alice:
"When I use a word, it means just what I choose it to mean -- neither more nor less."
'Cuck', within the world of Literotica's Loving Wives category, is a Humpty Dumpty word that means just what the LW Commentariat has chosen it to mean -- neither more nor less. 'Cuckold' means more -- there are many more of them -- the Cuck is one of its sub-species. But in Loving Wives the Cuck is a very special one of its sub-species.
The Cuckold
According to most dictionaries, a cuckold is the husband of an adulteress. In WEIRD* societies there's a lot of wives who have had adulterous sex -- one third seems to be a common estimate -- so there's quite a lot of cuckolded husbands. There are many varieties of cuckold, and there are many varieties of cuckold story.
The cuckold may or may not know about his wife's infidelity. If he does know that she's doing it, his attitude may be one of strong disapproval, or he may actively approve of her extra-marital liaison, or his attitude may fall anywhere between those two extremes.
He may or may not take some form of action regarding the wife and/or the man with whom she has committed adultery. If he disapproves, he may simply abandon the marriage, or he may take action to show her just how much he disapproves. On the other hand, if he approves, he may do things to encourage it. It may even have been his idea rather than hers that she should cuckold him.
No matter how much he knows, what he feels, or what he does about it, he has been cuckolded and he remains a cuckold whilever he remains married to that wife. Almost all Loving Wives stories have a cuckolded husband, as do several stories in other Literotica categories such as Inter-racial, Erotic Couplings etc. There are cuckolds everywhere.
Loving Wives stories will often chronicle highly innovative and entertaining actions taken by husbands to 'de-cuckold' their marriages. So far as these husbands are concerned, she has cheated and simply divorcing her isn't enough. She must suffer the consequences, and those consequences should be severe. They Burn The Bitch, or they Burn The Bastard who led her astray, in what are usually called BTB stories.
For the BTB mob; the authors, and especially for the commenters, there is no crime more heinous than a wife's infidelity. So the more violent and permanent the revenge and retribution wrought upon the Bastard and the Bitch, the higher the readers will score the story and the more favourable will be their comments. Even better, if the husband then finds a much sexier woman to replace the now dispatched cheating Bitch, the story is starting to look like Hall of Fame material.
She may redeem herself a little if she confesses and comes crawling back, debases herself entirely, suggests that the husband even things up by having an affair himself, and offers him undying fidelity from this day unto the end of time; but a story with a husband accepting a wife offering anything less will be classified RAAC - Reconciliation At All Costs - and it will be mercilessly one-bombed by the BTB mob.
*
Western Educated Industrialised Rich Democratic (WEIRD) Society is apparently the IN term used by sociologists these days to describe the sort of societies they do all their research in.
Thou Shalt Not Commit Adultery
When Moses came down from the mount with the Tablets, murder had one Commandment with Thou shalt not kill. But adultery had two. Thou shalt not commit adultery was backed up by Thou shalt not covet thy neighbour's wife* (along with the neighbour's ox, donkey, lawnmower, golf clubs and various other possessions).
Clearly, adultery is the much more serious crime. Not only should you not commit adultery, you shouldn't even think about doing it. Murder? Maybe, maybe not. Stoning an adulterous wife to death is probably a bit on the barbarous side these days, but BTB authors can devise plenty of other creative ways to get rid of her.
*
Presumably, God would have used the gender-neutral term 'spouse' if She was handing the Tablets to Moses today in these more enlightened times of equality and #MeToo.
It's About The Husband, Not The Wife
At this point, we should note that despite the definition of Loving Wives category stories being "Married extra-marital fun; swinging, sharing & more", very few LW stories really are about a 'loving wife' actually having her 'extra-marital fun'. The vast majority of stories are about the cuckolded husband, not about the adulteress wife.