Using and optimizing an alt tag reasonably is important for ranking highly for SEO because the search engine crawler can only recognize an alt tag. The search engine may skip your pictures without an alt tag. A large of proportion of image searching is via the search engine. Also, images are more acceptable to users compared to the text. Search Engines cannot see images on websites so that it cannot crawl the text either. So by creating an alt tag for every image, you have a great opportunity to let your image on a website to be as visible as possible.
