User stories are one-sentence requirements that are very effective at capturing stakeholder requirements.
The sentence is of the form: As a <role> I want to do something to get an outcome.
The user stories help business to focus on who does what for what reason. The how is not part of the user story.
A good set of user stories identify all the roles related to a system or an area. The user stories can be used to group different roles together to form all the roles that a single person or position would fulfill
A good set of user stories outline all the outcomes that are trying to be achieved. This puts an emphasis on the “why” things are being done.
The “What” is being done ideally will be just that, all the things that get done to create the outcomes. Oftentimes the “what” gets tied up with how things are currently being done. By focusing and refining the roles and the outcomes first, deciding on the “whats” becomes much easier.
For business, I find the user stories resonate with how they look at their business and therefore is an effective way to get a set of requirements quickly.