I don't see that nudes are necessary in photography.
If you are a painter or a sculpter then you have to do nude studies to learn the human form. But it's not necessary for photographers.
Why must nudes be deemed to be necessary. Why do they need to be to be seen as "studies" to be valid. It's still important to understand the human body no matter what the medium, be it paint, stone or film.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.