Why does the old fortune teller say that Santiago’s dream is difficult to interpret?

"And this is my interpretation: you must go to the Pyramids in Egypt. I have never heard of them, but, if it was a child who showed them to you, they exist. There you will find a treasure that will make you a rich man." "I told you that your dream was a difficult one. It's the simple things in life that are the most extraordinary; only wise men are able to understand them. And since I am not wise, I have had to learn other arts, such as the reading of palms."