Yes … already, come on! An interesting thing happened once on a blog post I did while the article was on page two the image I used in the post and included a good img-alt tag for ended up ranking #1 for that keyword in image search. It’s just less competitive and the point is that on page one a few images are usually shown and with the right image you can pull in more clicks than your page two article.
It’s also a requirement. You see those are needed t=for screen readers to read to a blind person.Its part of your sites accessibility to people with ADA needs. Which in the end a web crawler is like a blind person, so use the tag to show you’ve added yet another supporting element on the page for the keyword you’re after … and often others don’t use those tags so its your secret weapon sometimes.
I used this image to convey Citation Flow’s uselessness and the img alt tag supports that.