Placing images in cells can be difficult and most of the time impractical. You have to readjust all of the rows and columns. Your images need to be the same size unless you are going to adjust every row and column differently. Placing images in a comment is much more practical. When you place an image in a comment there is no need to adjust the rows and columns. The images are displayed only when you want them to show. You can use pictures of individuals to identify them. Spreadsheet data very often contains product and part number ids. Wouldn't it be nice to have a picture of that product or part number to associate with that id so that you know instantly what it is?