Barbie Doll Anatomy, aka Featureless, Nullification, Smoothing, Modest Nudity, Bandwidth Conservation, The Super Wholesome Space, etc.
People whose physical anatomy completely lacks any kind of 'private parts', be it nipples, genitals or an anus.
Physically they not only cannot perform the functions of those missing parts, but they also have absolutely no physical need to do so. Their health is unaffected despite only having uninterrupted skin and flesh where those parts should otherwise be.
Mentally they may have no capacity for sexual arousal or pleasure, or have no instinctive idea of what things like sex, breastfeeding or excretion are. They may also be completely oblivious to exploitation, having no concept of nudity taboos or inappropriate touching. Alternatively they may know about such things in others, but be unable to feel or do them themselves.
They may have once been normal but became like this, and either feel relieved or regretful regarding their condition. Alternatively, they might have been born this way and have never known any other kind of life.
Or it could all just be completely unexplained.