Answers to your questions give you more knowledge. That’s a given. But questions are often more important than the answers you get.
One of the most important reasons is to get the customer to relax. Asking easy questions allows you to establish a baseline for how to judge future body language signals he’s going to send. When he’s talking about his vacation, he’ll be leaning towards you, gesturing with his hands, smiling, and chin up. When you ask a critical question in a few minutes, he may lean away from you, cross his arms, put his chin down, and furrow his brow. These physical clues are more important information than any answers he may try to deceive you with.
By establishing a baseline for how he acts, you can determine which specific questions make him anxious, causes stress, or gets him to open up. Then you can adapt your presentation.