Sometime, people want to take a picture using their own camera instead of a cell phone. They really want a picture that looks like a photographer took it instead of an amateur. The camera will take a better picture. If you are a professional photographer, there will be times when you need to set up the camera and you need time to set up the scene.
Sometimes, the photographer will go back to the camera and the lens has closed. That is because of shutter speed. There is a shutter speed which if the camera has not been used during that certain amount of time will cause the lens to close. There are ways to set up the camera if you want a longer shutter speed.