Why would you follow someone else? Why did the people follow David? Why do people follow or belong to any group?
-- It is something you want to do.
-- You like that group of people.
-- That group presents some advantages for you.
-- You want to belong to some larger body.
-- The group provides you some sense of importance.
-- The group provides you safety.
-- The group provides you direction.
-- You do not want to be alone.
There are a dozen or so other reasons we could list.
If you admire a person as a leader you will realize that he/she demonstrates each of the above bullets personally to you: he/she (like you) wants to do the group activity, he/she likes the group and its members, and so on. At some point the leader gets his boots muddy with the same mud you are standing in. From time to time he is there with you, alongside you.
The leader is not thinking, "I want to be a leader". He/she thinks, "I have this passion I want to accomplish and I need these people and want these people to get it done."