I've always thought that camera film is unfair to models. Sure, it captures them accurately, in the sense that it is an exact copy of their appearance at one moment in time, but that's not how we normally look at them. When you see a pretty girl, you don't zoom in and scan her face for blotches and bumps--you wouldn't even be able to.
When we're face to face with someone we look mostly in their eyes, while just glancing at the other major parts of the face and probably focused more on them as a person than on their physical details, so we don't pick up small wrinkles and blemishes and our mind sort of smoothes out any characteristics that deviate from the norm; and it has often been said that pure normality is the definition of beauty. Retouching usually involves sharpening the eyes and removing distracting details so the end result is closer to how we would really see the model, sort of like how they say HDR is closer to how we would really see a scene because it takes into account our perception.
A raw, static image addresses only our analytical vision. Retouching is an attempt to add a bit of emotion.