“I was glad when they said unto me, ‘Let us go into the house of the Lord'” (Psalm 122:1).
(Note: I write as a Southern Baptist with little familiarity with how other denominations do their worship services. Therefore, what follows may be of limited value to some of our readers.)
Some tasks we cannot shunt off to someone else. Some key responsibilities we cannot hire others to perform for us. Leading the worship service is one of the pastoral essentials. The pastor is the leader.
This is not to say the minister will physically lead the hymns. (In some churches, he does, but in most someone else does this.) He will not pray every prayer or be the only one reading the Scripture or promoting upcoming events. But ultimately, it all goes back to him. The pastor is like the stagecoach driver. He does not pull the coach but holds the reins to the six horses that do.