"Is nude nescessary?" a photographer asked. "I think you can make a photo appealing without the model being naked" he said.
There are many kinds of nude photographs. Some are made to be sexually appealing and some are not. It is actually much easier to make a woman sexually appealing wearing accessories and clothes that helps to extol their body features than represent them purely naked who can only rely on poses and their actual body shape to extol their body features.
Every thing on a visual representation have a meaning. Through a dressed model you can tell, or at least have an idea, about the epoch, taste, age, culture, social class and even personality of the person photographed or of who the photographer is trying to represent, just by the clothes. The same with the make up, location and gestures.
When you want to concentrate only on the body form, texture and expression everything else become a noise, or a distraction. Even colours, in many circumstances give meanings and become distraction when you want to concentrate on shapes and texture. This is why black and white image are often necessary as well as nude images.
I don't mean that works focused on body expression and shapes has to be nude. There are many ways on trying to do it with appropriate clothes. But with clothes it will not be possible to represent and appreciate the full and natural body shape and texture.
It also doesn't mean it has to be a full body frontal nude, because the frontal nude are often a distraction too, depending on the level of appreciation, theme and the way it is represented. It will be sure a distraction for those who are not used to it.
In other words, not all nude or even frontal nude representation mean to be erotic or pornographic. We can also be sure that there are a lot of erotic and even pornographic suggesting images everywhere we look at in our daily life through advertises on TV, magazines and billboards that apparently sell services and products but after all they actually sell life style, which also include idealised sexual attraction and sexual power. Often it is too explicit to be true, so we accept it or just ignore it.