Power

If you're conducting a tour, the closest you get to power is talking about long-dead people who once had it. You'll point out where Washington spoke or where Kennedy was shot or where Marilyn Monroe once ate a sandwich. You'll wield interesting stories about them, but you're not exactly following in their footsteps in the power department.

 
I told you I was taking you to Disney. Here we are. (Source)

Well okay, so maybe you're literally following in their footsteps, but we mean you're not going to become president or a Hollywood star by relaying historical tidbits to children all day.

As far as the tour itself goes, it's not exactly the kind of place where you'll be exerting a whole lot of energy to keep people in line—not even when they're actually standing in one. Most people on a tour generally want to be there, and want to listen to all the interesting anecdotes you've said a hundred times (while acting as though it's the first time you've said them). 

The exception, of course, are kids, but typically you'll leave all the disciplining responsibilities to their chaperones.