Imagine you work in a hardware store. You notice a customer puzzling over the vast array of electric drills.
She turns to you and says, I need a drill, but I don’t know which one to pick.
You ask “So, why do you want a drill?
“To make a hole.” she replies, somewhat exasperated. “Isn’t that obvious?”
“Sure,” you might say, “But why do you want to drill a hole? It might help us decide which drill you need!”
"Oh, okay," and she goes on to describe the need to thread cable from one room, to another.