The prophecy, of the chosen one. And the fact that the dark side can never be destroyed. It’s an integral part of the force itself as a whole, and must always exist.

Think of balance as in stable versus unstable. Serenity. Peace. 

I sense a disturbance in the force. 

I sense great fear in you, young Skywalker. You have hate, you have anger, but you don’t use them. ~ Count Dooku

That is the very definition of unbalance of the force, with him at that time at least.

Even from an untrained Padawan you can sense that disturbance. 

Balance is the absence of disturbance that leaves the force unstable, unsettled. Like when you throw a stone at a pond. 

It has nothing to do with numbers or strength, but peace. 

There is no emotions, there is peace. 

Much to learn, you still have. 

I think by the dark side of the force Lucas always meant the force itself could be used in a dark way as in double edged weapon. Not that it’s a team that has to be balanced by the opposite team, otherwise it will be an unfair game. The force is a thing, that could be used for good, the light side of the force, and it could be used for and leads to and can magnify evil, if used another way, like the Sith use it. 

Jedi and Sith are not “taking” from the force, so when one side takes too much, they end up disrupting the balance. 

It’s the force itself that is in a state of unbalance, disturbance. As in upset, not mentally healthy and sane. This is from the view that the force is alive and has a will and feelings. Not just a physical thing that could be manipulated. 

Lucas could have said bring balance to the universe, but he kept insisting that actors say dark side “of the force” in the prequel trilogy, as opposed to just dark side like they used to say in the original trilogy, which could mean just being a bad person or evil. 

The force itself has a dark side. As in nature itself sometimes behaves as if it’s pure evil. And the Sith are using that dark side of the force itself, not the dark side of themselves, in order to become more powerful. 

The light side of the force is what the Jedi are exclusively using. That’s why it became light side of the force, as opposed to the good side only that was mentioned in the original trilogy. 

Like when Han Solo is sometimes a good person, but sometimes immoral. Same for the force. 

That’s why Luke was a good person despite using the dark side of the force sometimes. 

I do not fear the dark side as you do. ~ Anakin Skywalker 

Think of it like the ring of power Forged by Sauron, it consumes you, and turns you evil, even if it gave you nothing but power in the beginning. 

Cast into the fire. 

No. 

Destroy it! ISYLDUR!! 

The ring has it own will, own darkness. Same with the force itself. 

Wiping out the Sith does not erase the dark side of the force. It is always there, waiting to be consumed, to be used. 

The chosen one, because he is so powerful, will bring balance to the force, because he doesn’t need to move mountains in order to accomplish anything. 

That force sensitive conflict, war, erodes the will of all force users, and makes them in pain, suffering. Exhaustion. The constant pressure of war. 

That leaves the force unbalanced. Wounded. Depleted. Drained. Tired of all this. All the conflict and disturbance. 

The dark side of the force cannot be destroyed, at least without destroying the entirety of the force itself, both light and dark and everything in between.

The prophecy of the chosen one included destroying the Sith, not the dark side of the force itself.

You don’t know the power, of the dark side.

The power of the dark side of the force and using it, not the power of force sensitive beings when they become evil.

The chosen one, like Neo did, ended the war, and put an end to conflict, which restored peace, to the universe, and the force. 

What do you want? 

Peace. ~ Neo