I don't think we can ignore the fact that whatever we personally may think about nudity, there are stigmas surrounding it in society that might affect an inexperienced model in ways that they may come to regret, and I'm willing to respect that.
This does not apply to photographing property or landscapes, where the only substantive issue is that of commercial use. There is generally no shame associated with having someone's barn publicized, but alas, some people may come to feel ashamed of having their body publicized.
Should one give in in every case? No, I don't think so, but I can imagine cases where it would not be an unreasonable courtesy.