Now see what you've written here is a fascinating insight into this topic, and makes me realize why my opinion and approach is the way it is.
The idea that the LIs and other characters are NPCs, fundamentally, is true, right? They are non-playable characters. However, I don't believe the means they need to exist in limbo unless otherwise interacted with by the player, because to me the non-playable characters (and their actions) are as important as the player character, even in AVNs. Because, yes, while the MC is a conduit for the player and they are following things from his perspective, that doesn't, to me, mean that other characters are less important. I've mentioned this before, but when making this game I wanted the player to realize that the characters have their own lives and goals they're getting on with, and that while the MC is the main character, he's the main character of his own life, not everyone's else's. I felt like that was necessary to create a compelling story. I feel like it's hard to care about a character that feels one-dimensional, like they only exist to the extent that they're a part of the MC's life.
I'm not saying you're wrong or that my way of thinking is right, because at the end of the day it's just an opinion. But what you said did help me realize why there can be such a divergence of opinion for some people on the prominence of other characters in AVNs. 'It's not real life' - no, but in my case I want to present things relatively close to reality because, for me, that creates a more compelling story, more compelling characters. And that's my main priority.
And then to answer your later question, the 3 LIs who are virgins are Alice, Bonnie, Ellie.