Anyway, by default, 'Netorare enjoyers' are presumed to specifically insert as cucked protagonist because that's the PoV (which most at least consider annoying) and that's indeed what most do. I'm not denying that one can enjoy such works differently, as voyeur, to see such a train wreck happen but that's a minority
There are three problems with your assumption:
1) if you want to make that claim you would need data (surveys or something like that) otherwise you're basing things around your feelings.
2) there are plenty of ntr wich are from the pov of the fmc: accerola games, RaiOhGar: Asuka, Fox girls never play dirty (and other ADVANTGARDE games) or the Curse of Kubel are the first that come to mind.
3) If that were true then netorase, where the protagonist actively enjoys or willingly agrees to the cuckoldry, would outrank netorare in supply and demand. I say this because often netorares can end without knowing about the ""cheating"" or reacting with sadness and pain not arousal unlike in netorase, hell in some of them cuckholded never shows its face.
Thats without counting the plantonics relationships in netorares that have non-incestous brother-sister or son-mother dinamics where a bully steals their attention awau from the relative. There too much of a focuss on suffering in netorare, wich would appeal to a
sadistic enjoyment, to discard it as a minority withouth more information.
Ultimately this things could be answered by discussing the topic of ntr but from my experience that rarely happens. People who dont like ntr often have a hate bonner that compels them to insult ntr works and their consumers and no discussion can be happen under such hostility