Audience interest is directly proportionate to the presenter's preparation. You better spend time and energy on any presentations where the stakes are high. If you are trying to close a large sale or speak at a conference to an audience of potential clients, you better be ON your game. An audience can tell how much energy you spent on your presentation, which is a reflection of how much you valued their time. If they gave you an hour of their time, you need to make it worth it to them by treating their time as a valuable asset by making the content valuable to them.