In this blog post, Jeffrey Davidson discusses the fact that a common issue for Scrum teams is that their user stories are too big. He explains that many teams ask for larger stories because they don’t know how to slice the work into smaller pieces. Writing smaller user stories will make your team happier and more productive. There are many reasons behind the need for small user stories.
The first one is that developers need a sense of accomplishment and appreciation. People get frustrated when a user stories need many weeks or months to finish. There are also more chances to miss acceptance criteria, contradictions and implied requirements in large user stories. Those also implies a large conceptual costs to developing and maintaining mental models. Smaller stories make it also easier to prioritize or to control and change the scope of the project.