Should Ads In Adult Magazines Feature Naked People?

Reading some articles about advertising in different segments, I stated to wonder why ads in adult publications don’t feature naked people since contextually that would seem appropriate. Reading such a magazine, at least in part, is a goal-oriented activity — you buy a Playboy to look at nude women and skip whatever content doesn’t have them. If you ad features the desired content, it gets looked at. Kind of makes sense, no?
On the other hand, do those brands, and we’re talking about worldwide brands like Volkswagen, Seagrams and so on, why are the taking this risk? Or is it? I’m curious….