What if they don't do it right? What if they mess it up? What if they don't get it done at all? What if the outcome is not up to my standards? What if they do it better than I do?
Delegation is an area in which many leaders struggle. It's often hard to relinquish control. Others may not do it "our way". Many times it seems more expedient (and simpler) to do the work ourselves. Rather than learning to delegate effectively, we work longer hours.
By definition, leadership is about "leading" other people. The long term success of a leader is largely determined by those who follow. As a result, leaders must seek to understand what influences people, what makes them tick, how to talk to them, how to challenge them, how to motivate them and how to delegate the tasks for which they are best suited.