One distinct reason why Hughes' poem is featured so prominently in Hansberry's drama is because it shows the complexity of dreams, a dominant idea in A Raisin in the Sun.
Hansberry's drama was groundbreaking because she presented the issue of dreams for African- Americans in a complex manner. This was in stark contrast to the conformist and consumerist culture intrinsic to the 1950s. At the same time, Hansberry wanted to present an equally intricate view of what it meant to be African American. Part of the challenges that African- Americans faced in the 1950s was to emerge as human beings in a time period that locked them into convenient stereotypes. Hansberry challenges this lack of depth.
Using Hughes' poem works on both levels. The multiple visions of "what happens to a dream deferred" force people to look at things differently. After reading Hughes' poem, there can be no easy answers. Do dreams deferred "sugar over?" Do they "dry up like a raisin in the sun?" Do they "explode?" The reader does not know. As a result, they have to think and ponder. Triggering this reflective capacity is exactly what Hansberry wants to do in her drama. She does not want to present an easy answer. Rather, she wants the audience members to think about the characters she presents and how their dreams define who they are and what they do. When the reader sees Beneatha struggle to dream as a young woman of color, they see different visions of dreams emerge. When Walter fights against economic, racial, and psychological barriers to his own dreams, the audience must assess different elements at play. There are no simple and reductive answers. There is only the struggle to dream on different levels. Like Hughes' poem, nothing is easy. In referring to Hughes' poem in her play, Hansberry is accomplishing a similar poetic effect in dramatic form.
The poem's end theme is that permanent containment of dreams is not possible. The ending line of "explode" indicates that something will change. In much the same way, the ending of the play shows that the Younger family will not be deferred. They will not be contained. Walter "explodes" in a sense from his condition of constantly being deferred:
We have decided to move into our house because my father—my father—he earned it for us brick by brick. We don’t want to make no trouble for nobody or fight no causes, and we will try to be good neighbors. And that’s all we got to say about that. We don’t want your money.
In refusing to take Lindner's money, Walter and his family show their own need to "explode" in the face of constant being constantly deferred. The ending to the poem reflects a condition of change. In the same way, the play's ending is one of change. Walter has changed in acting for his family, who have changed in seeing that tomorrow can be better than today. In this way, the poem's theme is reflected in the play's conclusion.