I would usually argue that the speaker should always be in full control of his or her slides. They know the presentation best and, amongst other things, it will give them a chance to go back in case they forgot something or have to revisit an earlier point.
So I was surprised to learn about the recommendation to have a separate "driver" for the slides, i.e. someone whose only job it is to advance the slides in sync with the actual speaker. How and when does that make sense?