The Agile Manifesto says we value individuals and interactions over processes and tools, which is where the idea of “self-directing teams” gets its genesis. When an organization is feeling its way in bringing in agile approaches, there can be some stumbling along the way as they shift from telling developers what they are going to do, to telling the team (via stories) what needs to be built and letting the team steer the ship as they get things built. This might seem like a subtle distinction, but it can go a lot deeper than one might think.
Many developers have been used to being acted upon, rather than acting, when it comes to cranking out software. I’ve seen some rare occasions where a developer just doesn’t want the responsibility of making the decisions and prefers to not do Scrum. I’ve also seen teams where some prefer to just be given assignments, and the team accommodates them by parceling assignments as needed.
There are lots of decisions that management may have been used to making the past that can be shifted to the teams. The teams tend to make better decisions about how to create features, given they are the ones who have to do the implementation. The teams need good Product Owners (POs) so the teams understand the business objectives and have that constant interaction with POs to quickly answer questions as they arise. The bias should be to let the team decide.
This is why we take care to say the teams pull stories from the top of the backlog, rather than saying stories are given to the teams. THEY decide they can take on the stories, and THEY make the commitment to the PO that they are going to deliver in the sprint. So my Scrumism here is to say that whenever it is possible (and reasonable), decisions should be made by the team.
I saw a contra-example once. Several teams had been working together for a while and it was getting boring saying “Team 1, Team 2” and etc. They had a naming competition where the teams could come up with their own names. That really got the creative juices going–there were some really excellent team names being floated. Then someone in management got engaged, swooped in and declared names for the teams (comic book characters), and swooped out. Would have been much better, in my humble opinion, to have let the teams decide.