After Instagram copied the story feature from Snapchat, many apps quickly followed - notably Instagram's siblings Facebook & WhatsApp. YouTube & Netflix also have similar implementation although you definitely can't post a story on Netflix.
Why does this feature is widely copied? Initially, the self-deleting nature of Story meant that people don't put too much effort in publishing photos & videos. At this point, many users already felt the pressure to put picture perfect content in their main feed.
Being liberated from such pressure, users posted more content. Which in turn is consumed by many users. Since Story are presented in auto play mode - many users just mindlessly consumed it. It's also built for mobile from the ground up - shot vertically and displayed vertically thus consuming the whole screen. In short, it's replicating the behavior of people mindlessly watching television.
This behavior is golden opportunity for Instagram - they can add more advertisement without cluttering the main feed. They also keep users on the platform by disabling outside link except if you pay for it.
So that's pretty much the story of Story.