How was this not rated R?

There's a really great documentary on how films are rated and why (and the issues with it, in regards to consistency and otherwise) called "This Film is Not Yet Rated." But, the basic rules (there are exceptions of course) are a brief shot of nudity is allowed in PG-13 as long as it's not sexual and doesn't show the groin area. PG-13s also get one f*ck, as long as it too isn't said in a sexual context. So, "F*ck you" would be allowed once and still keep the film PG-13; "Let's f*ck" implies sex and would make it an R. And the amount of allowed violence in PG-13 movies is really an American thing. In "This Film is Not Yet Rated" they discuss how in foreign films, they're a little more relaxed about nudity and sex on screen and very strict with regards to violence. In America, it's the other way around - a result of the overly religious population of our country and repression in general to nudity and anything perceived as sexual in nature.