Its a matter of style (or the photographer's taste). There is a "look" that you see in the lad mags (Maxim, etc), but has been used by Playboy and even mainstream fashion magazines, that some might describe as being unnaturally warm. Remember the goal of these shots is to enchance the model's appeal, and a warm ("hot") look , suggestive maybe of being lit by a fireplace, or available (tungsten) light), can make a subtle statement. Most people would say that is more flattering than using a cold (blueish) or worse, green, light (althought I have seen that used effectively too, but with great expertise). I am certain that if you're seeing it in Maxim or Playboy, its intentional, in fact PB photogs regularly use warming gels on their lights to give those "orangy" highlights. While there are plenty of shoots using "normal" skin tones, as I said, its a matter of taste, and what the photographer is trying to communicate.
Another place you'll see warm skin tones, at least from me, is when I'mn shooting at sunset. As the sun sets, the color temperature goes down to a warm look which most people find flattering. When I turn the model around so the sun is to her back, I put a warming gel over the flash so the color temperature more closely matches the color of the setting sun, like this shot of Christy Hemme.
Regards,
Andy Pearlman
Andy Pearlman Studio