I think that Nathaniel recognises that his skill set is geared towards sex, and he enjoys being admired as a sexual object, because that is what he was taught. I want to believe that Nathaniel strips because it allows him to be admired sexually in a safe way and in an environment where he isn't made to feel less human for enjoying the attention. I want to think that stripping is part of him recovering and finding safe outlets for his needs and wants. Personally, I think he should get with Asher and have the relationship he seems to want. It would have the bonus of making Asher feel more involved and less frustrated with being kept out of everyone's beds!