Is it possible that there are women out there who are so beautiful and so alluring that doing porn would be a major step down for them?
I think so. Some women are divine works of art, like Emily Ratajowski. Her face and her nude form are visions of Heaven. Seeing some semi-evolved shithead shoving his dick into her would be a violation of all that is good. Emily is not slutty at all, she is simply Woman as God had intended.
I'd also put Kate Upton and Heidi Klum in this category. (I'd post pix but you all know what they look like.)