Many people have vivid memories of what they were doing when dramatic events unfolded (9/11 for example). Quartz published an interesting article on these "flashbulb" memories, named after their photographic qualities.
Emotions are a powerful anchor for memories. Obviously we don't want to invoke traumatic events to help the audience remember your pitch. But some element of emotion (an image, a story) is important to make your presentation more memorable.
Have a read through this chapter in my book to learn more.