imagine purpose as a string pulling you forward... your potential movement is much like a pendulum in this context... you may move left or right (lets keep it simple for now) left is less purposeful right is more purposeful.... so you move to right.... now you are pulling someone behind you and they see the same thing... left/right... so they go right... and so on and so on... now each one behind is on a "lower" scale relative to the higher perspective... so the length of string gets perceptually less and and less as you go..

Would this not appear as a spiral from an outside perspective? a "golden spiral" even?

imagine an infinite series of wake boarders to better illustrate this...