I guess there are multiple parts to this discussion.
1) Are we talking about voice acting all of the dialog, or are we talking about adding moans to the sex scenes? The former is considerably more expensive than the latter.
2) The degree to which porn style heavy moans are realistic.
The answer to 2 is complicated. There are literally billions of couples having sex regularly in this world, and there's unquestionably variety in how that sex plays out. I suspect that, without outside influences, the vast majority of women are considerably less evocative during sex than you see in porn. But porn does what it does because what it does is popular. And, I'm sure that there people who, having seen and enjoyed porn, have asked their partners to act differently in bed. That's not just being louder. It's also trying different positions and roleplays, etc. So, for good or bad (or both), porn influences reality.
In the end, though, WaL is more "erotic" than "porn." It skips most of the more extreme porn tropes, from incest, to beachball sized breasts, to abusive/forced sex. So, you'd expect that if they added audio to the sex scenes, they'd also skip the more extreme loud moaning.
This makes adding audio feel like a no win situation to me. The people who want porn-style moaning would be disappointed, and even the people who enjoy "realistic" sounds would probably notice that there are so few of them in a scene that they'd question how much the sounds really add.
In my own experience, I added sex sounds to a few of my games, but doing so was, by far, my least favorite part of developing erotic games. So, at some point, I polled my audience on what they wanted. I got a fairly even 1/3 split between, "I hate the sounds and turn off the audio," "I could take them or leave them," and "I really like them." Biased by my own dislike of adding the sounds, I chose to interpret that as "2/3 of my audience doesn't care if I stop doing sounds" and happily stopped doing them.
Tlaero
