@Handsoffisback
pelleas the specific question about why children need to be exposed to other people’s genitals has not been answered.
Several posters have pointed out the benefits of naturism that some enjoy.
No one has claimed it's enjoyable for everyone.
It is not about 'need' - we don't live our lives on the basis of only doing what we need to do. No family 'needs' a holiday in Disneyland, but that doesn't mean there's no justification for taking one if your family enjoys it.