#3b: A manager is not a full member of her team.
Managers are not part of their team the same way the people they manage are.
First, managers have fewer opportunities for daily connection. Bonds of trust are built through many small, repeated actions, and a manager has less access to these than a team member does with his peers.
Second, for an organisation to be successful, each manager must not only consider what is best for her team, but for what is best for her company. This can lead to misalignments between the wants of the team and the needs of the company. A manager's actions are not always best for the team.