In the Book of Isaiah Chapter 42 verses 1-9  we find the answer to why some are propelled and gifted to speak on behalf of the Lord. 

1)Here is my servant whom I uphold, my chosen one with whom I am pleased, Upon whom I have put my spirit; he shall bring forth justice to the nations.

2)Not crying out, not shouting, not making his voice heard in the street.

3)A bruised reed he shall not break, and a smoldering wick he shall not quench,

4)Until he establishes justice on the earth; the coastlands will wait for his teaching.

5)Thus says God, the Lord, who created the heavens and stretched them out, who spreads out the earth with its crops, Who gives breath to its people and spirit to whose who walk on it:

6)I, the Lord have called you for the victory of justice, I have grasped you by the hand; I formed you, and set you as a convenant of the people, a light for the nations,

7)To open the eyes of the blind, to bring out prisoners from confinement, and from the dungeon, those who live in darkness.

8)I am the Lord, this is my name; my glory I give to no other, nor my praise to idols.

9)See, the earlier things have come to pass, new ones I now foretell; Before they spring into being, I announce them to you.