A few random thoughts:
I've taken life drawing classes off and on for years, and my wife has never had a problem with it (she was an art major in college and also took life classes.) The interest in the model's nudity goes away quickly, even if she is attractive; you sort of get caught up in trying to get the relative sizes right, and it also because it's quickly clear that this is not a "relationship." It's learning a craft.
I've never asked my wife about nude photogaphy, because I'm not interested in it. I find 99.99 percent of it trite and boring. Actually, when I think about what that number means, 99.99 percent is not high enough. And I'm pretty sure that I couldn't do it any better. If I asked my wife, I suspect she might ask "Why would you want to do that?" She wouldn't have any intrinsic objection, she just wouldn't understand what I was trying to do.
I've looked at Photosig a few times, and, what can you say? Thousands of nudes at any one time, tens or maybe hundreds of thousands over a period of a couple of years. Almost any nude photograph you might be tempted to take is already there; and imitations of everybody. Maybe after a certain point in life (or perhaps I should say, after a certain number of relationships) nudity per se is no longer particularly interesting. (I also once wrote a book on Plastic Surgery, and during the course of the research, saw a few hundred naked people of all different shapes and sizes at very short range. That has an effect, too, I suppose.)
You'll also notice that when people talk about "great" nude photography, most of it was done 50-70 years ago. I mean, how many people have now shot nudes on a sand dune, and how many did we really need after Ed Weston?
I think most people now shoot nudes because they're mostly interested in their own reaction to shooting a naked person; we're not really talking about an interest in how the shadows fall.
A friend of mine has posed nude for "artistic" photogaphers who I think are pretty sincere about the work -- and when I looked at the shots, I thought, well, so what?
The great difference between photogaphing the nude and drawing the nude is that with photography, the capture of the image is ultimately mechanical. In drawing, of course, it's anything but mechanical. Human beings are exquisitely attuned to faces and bodies; if you draw one thing poorly, everybody can see it (John Singer Sargent once defined a portrait as "a picture in which there is something not quite right about the mouth.") So drawing the human face or figure is the ultimate test of skill; taking a life class is not only a learning experience, it's a testing experience. photographing the nude is...I don't know what it is.
JC