In order to optimize your site, you need to make sure you are including the keywords that you want to rank for multiple times throughout your site. Also, ensure your site has complete and up-to-date contact information, that you’re using appropriate meta tags, and that you include pertinent business information as text—not text on images that Google can’t search.
Another reason is that if you're using an image as a link, the alt text for that image will be treated similarly to the anchor text of a text link. However, we don't recommend using too many images for links in your site's navigation when text links could serve the same purpose. Lastly, optimizing your image filenames and alt text makes it easier for image search projects like Google Image Search to better understand your images.
This is not to say that small businesses can’t show within the top organic results. If your business is located in a less competitive market or industry, like a nail salon in a small town, you have a better chance of ranking high in organic results. Most small businesses find it easiest to rank within local results, though small businesses can also rank high in organic results by investing in search engine optimization efforts.