I believe saline is used for wound dressings because sterile saline helps clean a wound to prevent infections. The absorbent nature of the dressing allows the gauze to absorb.
Still, I believe that too much moisture or too little moisture can impede the healing process. For example, a new wound might still be oozing; therefore, an absorbent dressing may be all that is needed. However, if a wound is dry, then dressings that hydrate may be better. Nonetheless, always check with your doctor for accurate dressing advice.