Because if cultural standards were established based on the outlook of psychologically normal people, pictures of naked infants would never be mistaken for erotica. They would be taken at face value as pictures of infants, taken when they happened to have no clothes on--unless there was a damned good reason to think they were being used aberrantly.
As things are a couple in Peoria, Arizona sent their film to be processed at Walmart, including a few pictures of 2, 4 and 5 year old daughters in the bathtub... and ended up being placed on the sex offenders register. The mother was suspended for her job for over a year. The children were placed in foster homes for over a month. Fortunately sanity eventually prevailed but it is hard to believe that the children and their relationship with their parents will ever be quite the same.
And what got these parents in trouble was, ironically enough, their complete lack of pedophillic outlook. It seems that never occurred to them that taking a picture of their kids in the bath could possibly have sexual overtones. It never occurred to them that the pictures were too perverted to send for public processing. They never even realised that the pictures could be interpreted as pedophillic. And that is exactly how they ended up living the hell of being accused of being pedophiles who were sexually abusing their own children.
And that is why I sometimes think the pedophiles have won. Because to stay out of trouble every one of us has had to learn to look at a picture of a naked baby--and see it as they would and treat it is something illicit and taboo rather than the family snapshot that it actually is.
Judge Asked to Drop Nude Kiddie Pix Suit