Allusions can serve to display the author's experience or cleverness. They can show that the author belongs to a particular literary tradition or community, or that he or she is following recent historical or cultural events. Allusions often assume that readers will share the author's background knowledge. Therefore, they assert cultural standards and imply a generality of human experience that can evoke humor.
Certain events and characters from literature or history are used more frequently in allusions than others. For example, contemporary American literature often makes allusions to characters like Hamlet, Benedict Arnold, Mother Teresa, Judas, or Don Quixote. We allude to events like the Christian resurrection, D-Day, or the fall of Rome, and to works of literature like T.S. Eliot's "The Waste Land" and to Tolstoy's "War and Peace."
If you dislike or are having trouble understanding a work of literature, it might be because your background is so different from the author's that you lack the ability to understand the allusions. However, it is possible to enjoy a work of literature without fully understanding the allusions. Allusions can still evoke emotions without being fully understood, and you might be able to infer their meaning from their context in the literary work.
According to Adam Kirsch of the New Republic, allusions used to be exclusive because readers who didn't recognize them would feel left out. However, the Internet has changed this. Now people can easily research any allusions that they don't understand, and this levels the playing field for readers.