Yes, without a doubt.
Having an Instagram account helped me gain new readers. I had only 500 reads on my first story for a few months in August 2016/September 2016 before I had Instagram and it went up to 2000ish by the end of the year after having an Instagram account. It varies for different people and certainly takes time.
You get to engage more with your readers be it through picture posts, videos, comments, discussion posts, insta stories, polls, sneak peeks, etc. Sometimes, when readers read your story, there is a possibility that they tag you in their posts or screenshots and that certainly helps you gain new readers that might be interested in your story as well. You can also link your story on your Instagram bio. While Instagram is a wonderful place to start for self-promotion, it’s also a great place to show some love to your favourite authors/editors/artists/etc and also to form new friendships too. I’ve met a lot of wonderful people on there.
Also, not many people might be aware that our stories exist unless we made some announcement about it like on the forums for example. Not everyone uses the forums. Some prefer forums, some prefer Instagram while some have both. So having an Instagram would help you reach a bigger audience.
Hope this helps!