In Hierarchy it takes just one manager to define a strategy or a goal. Then the manager can find a way how to sell his strategy and how to motivate people to implement it. With all the good will, people understand the same message in different ways, so the manager is still needed to monitor and correct implementation direction. The hierarchical system makes it easy to make a decision, but to turn the decision into a reality that is in line with the goal, the manager is needed. If the manager leaves the environment for any reason, the end result won’t be what he envisions, or the entire strategy will be abandoned.
Defining a goal or a strategy in a management system without managers will be a longer process than in hierarchical system. Identifying a strategy will involve more people with a different perspective of reality and different thought processes. When a group agreed upon a new strategy though, they will execute it in a way that the result will depict the original goal. Event if overtime the entire team will change (not at once), they will reach the common goal.
Like all of you I’ve seen and experience all the time, a new direction dictated by any authority (supervisor, manager, executive) just to be overwritten by a new authority after several months (in the good case). Letting groups manage themselves and organize themselves is a better long-term approach than getting short-term solutions that will be replaced by a new short-term initiative.