Instagram stories was introduced a few years back and ever since has been one of the most used features in the app.
The main reason being that it is a way to connect with your audience more closely and share updates from your personal life, etc.
Stories are one of the most important parts to nurture your gained followers and keep them engaged.
When doing this your audience will start replying to stories, DMing you, having more trust in you and being ready to buy from you.
And stories are also one of the best ways to sell on Instagram!