I wondered that as well... The only thing I can think of, and keep in mind this may be in my head or a coincidence... is that when you create a larger chain, more wild tiles seem to appear afterwards. Maybe points have something to do with the likelihood that more of those will appear when the ones you used in a chain are replaced from the top?
I hope someone with concrete explanations shows up soon, because that's just a theory of mine, though it seems to occur every time I do it.