In much of human history, dreams have been seen as portents, signs, omens conveying trustworthy information about what was and what was to come. As an example of this, there is a famous incident told in Genesis 41 of the Torah, also called the Bible, in which Joseph interprets two dreams for Pharaoh while Joseph is imprisoned in Egypt. Because Pharaoh dreamed and as a result of Joseph's dream interpretations, Pharaoh prepared his land for seven years of famine following seven years of plenty--because he believed them to be a true portent of what was to come.
In Gilgamesh, the same attitude is revealed when Gilgamesh has three dreams and his wise mother interprets them for him. When he dreams, he immediately seeks an interpretation as he believes his dreams are sources of information about his life and the world round about him.
Gilgamesh got up and revealed the dream, saying to his mother:
"Mother, I had a dream last night.
Stars of the sky appeared,
You loved him and embraced him as a wife;
and it is he who will repeatedly save you.
Your dream is good and propitious!"
There are many in contemporary society who still believe in the portent of dreams, in fact, Freud wrote a great deal about dreams. What is different, though, is that this contemporary belief in dreams and desire for interpretations is no longer a central cultural practice as in Gilgamesh's time; it is now a subcultural interest and activity. In addition, those who know how to interpret dreams are not as plentiful as they once were.
One significant difference is that dream interpretation was an official occupation and science. The courts of both Egypt and Mesopotamia had specialist dream interpreters and in both locations an extensive literature of dream recordings and interpretative systems developed. More often than not, it was the king's dreams that found their way into the epic and historical literature of the times, although the Gilgamesh epic also contains Enkidu's dream/s about his forthcoming demise.
On both occasions that Gilgamesh dreams he requires an interpreter. The first is his divine mother Ninsun, and the second is Enkidu en route to the cedar forest. In the latter case, I can’t help but wonder whether Enkidu’s unlikely and consistently encouraging interpretations are designed to poke fun at official dream interpreters. In the standard version of the epic (as opposed to the Old Babylonian version and the earlier Sumerian poems) there is a more critical understanding of the expedition to the cedar forest. Not only does it result in the displeasure of Enlil, but it leads directly to the death of Enkidu. Despite the pair's success in slaying the divinely appointed forest guardian, the ominous nature of the king's dreams may anticipate these later, unfortunate consequences. In this context, it’s not hard to imagine the editor deciding to ridicule unquestioning support for misguided military expeditions by court appointed dream interpreters.