They can help keep things organized. This helps the reader with a screen reader to understand that a list is on the page. If you use actual numbers on the list instead of using the list tags the screen reader can read the numbers. This allows the user to know that a list is there. Take a look in the Graphics Reference section to find places that you can get these graphics.
Many screen readers have a difficult time telling the user that the horizontal line is there.
Using a graphic instead. One elegant way to solve this problem is to use a graphic with an alt tag. It will tell user with screen readers that there is a horizontal line there, and it will give your page a distinctive look. Take a look in the Graphics Reference section to find places that you can get these graphics. Images and Image Maps Images Meaningful use of images is important.