The previous thoughts were well articulated. The idea of consolidating power drives the superpower war. The late Howard Zinn entitled a chapter in his work on American History, "A People's History of the United States," as "War as the Health of the State." The premise here is that nations benefit greatly during wars as it helps concentrate power in the ensuring of complete civilian submission. Indeed, Orwell's conceptualization of the nations at war helps to underscore the idea advanced that the government of Oceania is one that functions when the public is completely submerged under the weight and force of authority. Being able to keep the public in a state of constant submission with wars being waged helps to accomplish this goal.
Going along with some of the previous posts, particularly post WWII but certainly in many societies prior to that, there was in some ways a great pressure from industrial investment in the production of war material for it to be used. You couldn't ask industry to switch from peace time to wartime production and then suddenly have the war stop. What would happen to all that equipment and investment?
This gets long in the conspiracy department, but if you don't believe that powerful wealthy corporations and indivudals influence government decisions...
Along with this is a huge part of what the previous post says. In order to maintain control, an outside enemy is very helpful in diverting attention away from domestic problems. People put up with the idiocy of airport security theater because we are told that if we don't terrorists will rule the skies.
The basic answer here is that the superpowers need to stay at war with one another so that they can keep their societies the way they are. They need to have constant war so that they can continue to have hierarchical societies. Constant war helps with this because war is able to
use up the products of the machine without raising the general standard of living.
If the war did not continue, all the industrialization and such would raise people's standards of living. The factories would crank out consumer goods that people could enjoy. But if this happened, people's lives would become easy and people would become more equal. This would destroy the hierarchy that the governments need to maintain in order to keep control over their socieites. We can see this in the following quote:
For if leisure and security were enjoyed by all alike, the great mass of human beings who are normally stupefied by poverty would become literate and would learn to think for themselves; and when once they had done this, they would sooner or later realize that the privileged minority had no function, and they would sweep it away. In the long run, a hierarchical society was only possible on a basis of poverty and ignorance.