For most preachers (including myself), providing more than one illustration in a sermon is difficult, if it is done at all. But no matter how difficult it is, it must be done because it helps the listener process the principles, providing more clarity to the meaning of the text.
Illustrations are difficult because they require preachers to shift gears from excavating the text and laying it out systematically to discovering how the texts principles relate to life situations, whether it be theirs or someone else’s. This “shifting of gears” is often difficult for those who think in logical patterns and systems, which are taught and re-enforced through their reading patterns. By spending more time reading theological treatises, which present material systematically and logically, rather than works of literature, which reveal its truths through stories, preachers are training their minds to follow logical patterns and lay out systematic grids, which is not a bad thing, as long as you recognize the intellectual development that is occurring. As a result, preachers (myself included) find it difficult to make the shift to thinking in terms of narratives and stories. This difficulty of shifting from one job to the next is often why preachers neglect the task of illustrating.
Going further, illustrations are also neglected because they require the preacher to “delve to that level of being where mind, soul, body, world, and psyche are real. Until he has done so – until he has plumbed the depths of his emotions, relationships, and experience and integrated what he discovers in those oceans with what he knows intellectually – his own understanding is not complete.”  To delve to this level takes work. It takes hours of thinking, working, and re-working an illustration until it is just right. It requires one to go the extra-mile intellectually. Neglecting this extra work may prove one to be intellectually lazy.
The Purpose of Illustrations
The purpose of illustrations is to make the abstract, real, or to make the foreign, familiar. Truth is best understood when it is observed in the context of a human situation. This does not mean truth is only understood through experience, like many post-moderns would claim, but it does mean we best understand a truth when we are able to work with it, see ourselves in the situation, or relate it to an experience we have had. Illustrations allow us to do just that, they “provide the mechanism for this life-specific understanding and are thus indispensable to effective preaching.” 
As preachers, we must understand people do not make decisions simple because they have the intellectual knowledge. Rather people make decisions when they can see themselves in the situation.
If you have ever been hesitant to move to another town for a job, even though you knew it was a better position for your career and the town was better for your family, you know what I am talking about. You may have had all the facts in front of you, but until you actually met your colleagues, toured the facility, and walked the streets of your new neighborhood, you were not really convinced the new job and town were better. Why?
“Because we best learn and make decisions when the abstract is made concrete.”
Bringing what is abstract into the concrete is the purpose of illustrations. As preachers, we want our people to be able to see themselves in the situation, to experience the principle of the text at work, so they will understand how their lives need to change, or how the principle relates to their world. Bryan Chapell says, “Because life-situation illustrations provide this experiential data, allowing individuals to “live through” the implications of their spiritual choices, they well serve life-changing preaching.” 
Illustrations are difficult to incorporate into a sermon, but they are necessary. Without illustrations, our people in the pew will not fully comprehend the meaning of the text, nor will they understand how the text applies to their lives.
In other words, without illustrations we are not providing full-fledged communication. By linking the text to experience, illustrations “make the Gospel real, fleshly, and interpretable.” . This means illustrations are not a side-show used to make the text simple for simple-minded folks; rather, illustrations are a necessity for communicating the whole idea of the text. They are what add depth to our ideas and motivate our people to change.
So the next time you think about skipping out on an illustration because it would require too much effort, think again. Your extra effort may just be what you and your people need to fully understand the text and be motivated to change.
 Bryan Chapell, Using Illustrations to Preach with Power, 59.
 Ibid., 49.
 Ibid., 62.
 Ibid., 59.