People don’t simply buy a product just because they need it. It is clear by now, that they buy a product to satisfy a need. The key question to ask here, is “Why does the person have a need?”
For example, a couple currently owns a 2 mid-size cars and were recently blessed with twins. Considering 2 additions to the family (a big change), the couple identified a need for trading one of their mid-size car for a family van. Look beyond the need, identify exactly what is changing, why the couple is seeking for a new vehicle. If the salesman is trying to sell the most appealing sports car to a couple seeking a bigger vehicle to fit their family and convenience, that doesn’t satisfy their need for the change they are undergoing. Reasons for change would be appealing differently to different people. People may be trading their old car for a new one possibly for more reliable transportation, maybe their family is expanding, maybe they are looking @ better mileage, or how about status or image?
Reasons would be numerous. Cater to the change that has caused the need, satisfy the need, solve the problem, and you will have a product that sells well.