With respect, I could not disagree more.
IMHO a game/story/AVN about a son who is "betrayed" by his corrupted mother (or sister, etc) makes much more sense to me if the son does not lust after them. In a fatherless family the son (especially if his only/older son) often sees the rest of the females in the family as:
A. Pure and virtuous, devoid of any carnal desires of their own. (My psychological guess here is since the family has already missing one parent, the son needs the other to "stick to their role" more than if two parents are present and functioning.)
B. Under his responsibility, the "man of the house" fantasy.
An NTR AVN/Story kicks both aforementioned assumptions in the balls, hence giving pleasure to the players/readers.
Adding incest-lust into the mix, more often than not makes the already challenging task of creating realistic NTR and Incest scenario, both complex tasks to pull off realistically, collapse under a burden of unrealistic behavior. In other words: it's either a son lusts after his mother story or his mother fucks around story, but combining both elements in a realistic manner will usually create messy results.
For sure. In that same vein, I personally don't believe in the NTRness of a Chad MC having optional NTR (not whoring out/alpha sharing, but getting shafted with real NTR). Well, both Chad MC and Incest scenarios can include NTRish things, but that kind of story would only work for me if it's not fetishizing the NTR side nor the non-NTR side and just telling a grounded story.
But most stories tend to be quite porny, thus, I need to make up my mind about what kind of narrative I'm navigating. If the general idea is that the MC is, or going to be, some badass/hero/chad/harem collector, picking some choice that lead to his wife/mom/whatever getting corrupted behind his back doesn't jive that well with the overall intention of my playthrough. Similarly, if I'm trying to do an NTR run, but the MC is going through much of the same development of a harem hero, it kind of conflicts with a smooth NTR progression arc.
The set up and story beats that make up the flow of a "hero rising" narrative vs a "NTR corruption arc" are just not really compatible using the same common node plot structure. To do both of them justice, I feel like it would need to be almost 2 entirely separate scripts. If there isn't much of a story in the first place, I guess it doesn't really matter that much though ha.
Anyways, I initially thought the OP was talking about mom NTR in general, like saying mom NTR isn't NTR and is just distracting, but maybe they were talking about literal incest like the male MC lusting after the mom and having a positive incest route in an NTR game? I dunno.