The costumes are about movement, not simply about the dancer's BODY.

Fringe, for example, might make a dancer's silhouette look "bulky" momentarily, but it also elaborates upon the movement of her body - as do (well)draped elements.

The be-all and end-all of costuming should not be to look slim.

As for the nude stuff - yeah, that gets a little weird. Nude should not be used in places you wouldn't actually show skin. It should be reserved for areas where "high/low-cut" is a little too high/low for safety, or under lace.