Believe it or not, cynicism surrounding duck and cover back in the 50s was a communist ploy. It was the cold war version of demoralization.

When bomb yields were in the kilotons, there was a shot at our country surviving and recovering from a nuclear war. Soviet bombers were easy targets and we could have defended ourselves with a relatively low amount of damage nationwide. Duck and cover was used to help prevent serious injuries outside of the "instant and assured" death zones.

If people weren't trained to duck and cover, they could have been hit by all sorts of flying or falling debris. These kinds of injuries would clog up hospitals. Duck and cover helped mitigate these kinds of problems.

Of course, as the years marched on, bombs targeting cities grew and carried yields in the megaton range. Duck and cover does seem kind of pointless in that scenario. Even if you were to survive the initial attack, the radiation from a modern nuclear war will certainly make life miserable for survivors.

Still, for a short period of time, duck and cover was a pretty sound strategy for civil defense. In conventional war or natural disasters like earthquakes and tornadoes, it certainly doesn't hurt to follow those rules ... flying debris and partial structural collapse can fuck you up pretty bad ... Having something ... Anything over your head could be the difference between life and death.