Why did Campbell Scott agree to appear naked in this? Good film, though

I love Campbell Scott, I have watched his entire filmography (TV shows included) and I've noticed that he's pretty much avoided full-on sex scenes in his films (the furthest he'd gone is merely a naked chest), and yet he accepted to appear fully naked in this film (his genitalia covered by sheets, of course), in a post-sex scene in bed with a clothed Lizzy Caplan (at 01:01:35). Why'd he do that, especially as his lack of pants added nothing to the plot? Was it because Crashing is a low-budget film and he knew not many people would watch it? So he took a safe choice to do so.

I liked the film a lot - minus those random scene portrayals by complete strangers. The plot of the movie kinda reminded me a bit of a Chuck Palahniuk novel. I enjoyed the witty, unpredictable dialogue blended with some academic language.
Were Kristen and Jacqueline only his imagination as part of his new novel?