All the images you use on your website can be helping you. Most people when they add images to website they simply add the image and forget about it. They dont take advantage of the alter text and tags that can be setup. Its like having Brad Pitt as your wing man and not having him talk you up. Its crazy.
When you set up these tags and text for the images web crawlers see that as well and it helps your ranking. You need all the help you can get with exposure and this is an easily missed thing that would improve result now.
Another reason to do this is if you have blind people viewing your site they utilize apps that reads the text and any alt text to them. It could help them get a better picture in their minds of what it is that your site is about. You’re already posting the image you can spend another minute to set it up correctly for your SEO and your audience.