BUT WHY?

 So Robert Cialdini explains that humans like to be given a reason; we like to hear a "because". But his only explanation for this is that it is somehow hard-wired into our brains.

I don't know. I've been paying attention to how I feel differently when students ask "Can I go to the bathroom?" and when they ask "Can I go to the bathroom because ...". And I am beginning to form a hypothesis of my own.

I think that when a favor is asked without the "because", I (we) assume a reason ... and it's typically a negative assumption. 

Student: "Can I borrow a pencil?" 

        Me: "Why? - because you came to class unprepared?"

        Or: "Why? - because you lost yours?

        Or: "Why? - because you're too cheap to buy your own?"

This means that a student with a "because" handy can kill my negative assumption before it's even born: "Can I borrow a pencil because mine has gotten too short to hold in my hand?" 

Not only does this preclude my negative assumption, it hits me with an implied compliment in presuming my reasonableness. 

This need for a "because" may seem insignificant at first glance, but I am getting the impression it is bigger than we imagine.