Why does Langston Hughes utilizes similes and metaphors in his poem "Harlem: A Dream Deferred"?

Anything deferred is set aside, delayed or abandoned for whatever reason. Things that are neglected soon begin to resemble the objects in question. A raisin in the sun dries up A sore unattended will become infected and fester.Rotten meat? Well you get the idea. Dreams deferred at best are put in limbo and we never know what we might have accomplished had we pursued them, At the worse they fade into oblivion never more to return.