Why didn't the poet use simple language?

Today, one of my students asked me why did poets write poems in languages that were difficult for the students to understand. He said, "Why didn't the poet use simple/straight forward language?" It was a straight forward question and I tried my best to satisfy him with an answer.

I told him to compare two sentences:

1.   "I miss you" 
2.   "I miss you like the dry earth misses the fresh showers of spring. "

I asked him which one did he like.

He said that he liked the second sentence. I asked why and he said the second sentence was more beautiful and I asked him why again and he said because the second sentence was talking about spring. 

Then I told him to close his eyes and listen to the second sentence when I read it. I asked him what pictures did he imagine when he heard the words. He told me that he saw the rain in the spring. I asked him what else did he see and he said, "flowers". I told him to imagine the rain on his face and asked him if he would like the feel of the gentle rain in spring when feeling hot. He said "Yes". Why? "Fresh feeling". 

So, I told him that the language used by the poets are far more beautiful than the other language one reads in other forms of literature. The words used, create pictures in the reader's mind and touches the soul. The images used, arouse emotions of love, romance, happiness and sometimes even loathing. In this case, the intensity of missing the other person is compared to the dry earth and its happiness when receiving the fresh showers of spring. This is a powerful image if we are imagining the words. So many emotions/feelings are aroused if one tries to imagine: dryness, heat, beautiful spring, freshness, and the gentle rain.