Each layer in the hierarchy must add just the right amount of detail. The exact amount of detail each layer must add depends on factors such as the complexity of the business and it's environment, the depth and breadth of the organizational hierarchy, and the complexity and intellectual content of the activities which must eventually be performed.
In this way, leaders are able to work in terms of visions, strategies, high level plans, principles policies and other abstract concepts, trading of competing and subtle agendas, whilst workers are able to deliver very specific, tangible activities.
If any layer in the hierarchy adds too little detail, their subordinates will find it difficult to understand the organisation's strategy and what they are expected to do to deliver it. On the other hand if any layer provides too much detail, then the layers below it may feel disempowered and disengaged.
Sun Tzu advises that we should manage many as we manage few. Organizational hierarchy is an important tool in achieving this. Whilst many people consider middle management to be an an obstacle to effective communication between leadership and the workforce, I think they must play a vital role in translating strategy into implementation.