I heard this is a Japanese thing. That people are so afraid of public opinion this actually works. I hope it's just bs, pretty bad if true.
Yes, some part of is because of Japan and it's social pressure. For example train molesters do sometimes get away with shit because their victims on the train don't want to be a bother to the other passengers.
For one the writers of a good number of these games are usually just good artists and not great writers. I also understand a wish to be brief so that you don't spend an hour playing through the game with no sex scenes, as I have unfortunately been cursed to continuously endure due to both my playstyle and the ever growing list of "bunch of fun porn games that I want to really play, but just want the sex stuff for now." Unfortunately the best mix of "Satisfying visually and storyline wise," are usually hard to find thanks to the medium being choked with low effort garbage. And some of the high effort stuff is MTL which I can't translate.
Back to your point, I do think I know what some of the worst feeling NTR is like, and that's from ScaleGarden. Great art, great build up, and then out of nowhere there's a sudden escalation, usually by someone who wasn't even built up, and thus comes right out of left field. Personally the latest ScaleGarden game, when I was playing it felt the worst and felt strangely lazy with the usually great buildup before the disappointment.
The reason for the husband not being involved in the story or even not being present at all is because while NTR is popular what's more popular is stuff with the dressings of NTR. "She's a wife, that's 5 times hotter than someone her age that's not a wife!" These stories are basically just corruption but with the plot device called a relationship that is purely there just to:
1. Give her a reason feel bad about the corruption besides the corruption itself.
2. Involve NTR situations and plays that aren't possible without a unwitting participant.
3. Make it personal. While the woman could be corrupted normally without a lover, adding one even if they aren't focused on gives the woman an easily understandable goal and maybe even reason for their corruption.
4. Make money. NTR situations even if it's the flimsiest non-NTR NTR you've ever seen sell gangbusters. Vanilla and Corruption sell too, but because it's so easy to formulate a popcorn NTR game; as long as you aren't too ambitious it can be low cost to produce and high profit.
I'll tolerate the tired tropes in short form, like a <40 page comic if the art is good and I enjoy her reaction to the process, but once the story becomes more flushed out or requires engagement (like in an interactive game) that stuff grates on me too. Too many writers jump straight to the full, violent rape scene rather than a slow boil corruption story. The initial setup of, "Your boyfriend/fiance/husband doesn't have to know, it's just this small kiss/pose/BJ, and you REALLY need this money/food/medicine/magical relic key to saving your race/village/nation/world" is what I want in my erotic fantasy RPG.
I get this so hard. My first Norn game was only like a year ago and I thought I had skipped some scenes or something. It's a pity, I wanted to read/play through the increasingly erotic situations and art in those games, only to find out it's just a veneer to just instant slaveplay. Which I wouldn't have a problem with if that was what I was looking for, but it wasn't.