If you were somehow given the choice to predict the behavior of one of your friends or a complete stranger, with your life in the balance, which would you choose? You would probably choose your friend, right?
Ok, so the answer is obvious. Of course you would choose your friend! What isn’t so obvious, though, is the reasoning behind which we make that choice. Put simply, it is something like the following: by observing past behavior we can better predict future behavior, and this results from people being habitual creatures.
Given this, why do we reinvent the wheel so much in design? Why are we coming up with so many designs that must (or should be) be “tested” before we actually know if they work? Can you imagine if we were paid according to the actual effectiveness of our web design, and not the hours we put into it?
When this does come to pass, when we are paid on the efficacy of the design and not the hours we put into it, we’ll see a lot more features that aggregate past behavior in order to predict future behavior. It’s what we do all the time, just not in web design.