The conparison of a still small voice to wind, earthquake and fire I think is because we look at God in his GREATNESS, AWESOMENESS. MAGNIFICENT, AND MIGHTY, that his voice matches his character, that his voice would roar like thunder and it could but he knows that would frighten us, so the sweet still voice we must learn to listen for, with all the busyness of the day Gods voice is what we need to train our ears to hear.
His voice comforted Elijah by letting him know that he was now alone just as we sometime think we're the only ones going through this problem or that situation whatever were going through is forr a reason, a repositioning as he did with Elijah for something greater.
We miss the still small voice when we are complaining, stressing over situations and even listening to someone else voice.