Wonderful philosophical question this.
In fact when we put on the light, the darkness instantaneously vanishes. We need not ask the darkness to go.
The absence of light is darkness.
For observing any thing or being, we require our eyes (of course with our mind in attention) and the object. But the object is only visible when there is light. The object is not visible when there is darkness. Light is important for keenly observing the internal nature and external world.
That is why it is also called 'insight' when we look inward.
Our mind should be bright (light), sharp, steady, stable, strong, pure and simple. All the words used here are important.
Light is therefore important. 'Vision' is also an important word in discussing this point.