Leadership can suggest something good or bad. When David went on missions to kill Philistines for example, that was good leadership. When Hitler had a mission to kill Jews, most people now recognize that as bad leadership (morally bad leadership). The point is that both David and Hitler both put their hearts, minds, and souls into what they did to exterminate the enemy race through the use of others, but only one could be said to be a good leader.
Sometimes the bad part of being just a servant is that the servant just does what he or she is told to do without really thinking about things to carefully. Both good and bad servants exist, but servants would often differ from leaders in that a servant does not share ideology, world view, beliefs, and plans with the master in many cases. In most retail establishments for example a manager would have to vocalize a belief in certain doctrines that a company holds important and the manager would be aware of company plans before anyone else, but an ordinary servant would never be a manager no matter how skilled unless the person had a certain world view and prescribed to certain doctrines.
Many people have highly considered me for management positions in many different companies, but every single time people learned that I am not just a standard pew sitting Christian all my opportunities would suddenly be taken away. Most everyone that I have worked with has appreciated me for being a hardworking person that works very diligently, but when they ask questions about why I went to school or what I am going to school for, people would shutter and shut down when I would give truthful answers. Overall, I would have to be completely dishonest to say that I am going to school for some other reason except for God.
When people decided to have a separation between church and state, this caused the need for a party to judge between the two that could be considered neutral. The neutral party containing atheists, agnostics, and people that are not at all zealous became the governing class to ensure that everyone had religious freedom. The neutral class soon became the choice party for all businesses and offices that involved serving other people. The problem is that most of the people that are zealous find themselves serving the neutral party outside of the elite industries such as higher education, political office, professional sports teams, and other such places that employ the stars of society. The leaders in secularism thus are required to never express faith in public for fear of legal, political, and other repercussions that could reduce the flow of money into a business.
The only people that can be secular leaders and church leaders at the same time are people that reduce the message of the scripture into a message of humanitarian aid open to everyone, people that say that all gods shake hands in agreement, or people that agree that the message of the gospel is not as important as all other things (such as a recreational affair). One time for example an employer looked at my resume and then told me flat out that in order to work for him that my job had to be the most important part of my life. This means that family, Christ, and everything else would have to come in second to my job.
When I was between six and twelve years old, I would shovel gravel for my father after school until the sun went down. When I was in early grade school, I went to school every day despite the fact that a gang of kids from Chicago would kick me in the groin for hours after school almost every day for years. Despite proven track records to outperform other employees today and despite the education of ten years of college, a secular employer would be extremely unlikely to put me in any leadership position because even my education marks me out as being sincere about a belief in Christ. The overall point is that if a person is just a standard servant, then they can get away with having the freedom to believe the way that they find themselves compelled to believe, but anything more than that is much more different.