By cropping a picture, you can change not only the focus or subject of the picture, but also the mood. You might be amazed at how you can transform a picture simply by cropping it. (microsoft.com)

Here you specify left, top, right, bottom margins to be cropped off the source image. This mode is optimal for processing documents after you have scanned them, e.g. if you need to crop margins off scanned images or change size of raster images. (imageconverterplus.com)

While the temptation might be to delete such images the beauty of shooting in the digital format is that editing images after shooting them is relatively quick and easy. Cropping is one option for fixing such problems. This is usually done in photo editing software (most cameras come with software that will enable this) but these days many cameras can also do (digital-photography-school.com)