Imagine that you're standing halfway down the steep slope of a crater. You want to get to the halfway point of the slope on the other side of the crater. You could walk down the slope to the bottom of the crater, then up the other side until you got halfway up. But that would take a lot of effort.
It would take less effort if you stayed on a ledge at the same level (not moving up or down the crater) and walked around to the other side. Sure, it would be a longer walk, but you would be exerting less energy. You'd be taking the path of least resistance.