I can only speak from a student standpoint about this, but the confetti offers a nice pat on the back for me and my fellow students. We especially appreciate the fact that different items are rained down in the confetti, and we often brag to the others about whatever we received that day. The more abstract the item, the better we tend to like it. To be honest, I really wish there were more options in that area.
I know it serves little purpose, but that little purpose sometimes can create internal satisfaction, which can often drive us in ways we tend to overlook. Granted, the confetti hardly drives me to turn in my assignments on time, but I often theorize that the items within the confetti change in accordance to how early they are. I like to get the ninjas. I like to infer that that means I was incredibly fast at my assignment. How fast? Ninja fast.