Although i realize (sort of) why lighting is important i don't think that its as big a deal as things like Sound & Colour.
With sound and colour you can change a scene, and now, while watching films I see how they come in useful. Colour can be used to help the story along by having certain colors for certain things like in 'Saving Private Ryan' i found that warm colours like yellow, orange & red were used to symbolize home.
'The Dark Knight' used a violin (I think its a violin) in any scene the joker was in or was going to be in, to show hes near.
Lighting is obviously good for getting a certain shot (found that out today, when recreating Bohemian Rhapsody) also get across certain moods (mostly Scary)
I will probably find it very useful later on in life, but for now i feel its just not a big deal in comparison to elements like Colour, Sound, Composition........