If you search for the greatest small forwards of all time, players who make the list are among some of the best players of all time at any position. I would say small forwards are not only pivotal, but essential, to a team's success.
Usually, when players progresses through youth leagues their coaches will group them into two categories: Short and Tall.
Coaches will make the shorter players guards and the taller players forwards. Although I think the split is an antiquated way to divide players, I believe it led to the development of the small forward position.
When coaches talk about "matchup nightmares" usually they are talking about the small forward position. Some of the early youth league guards grow to be much bigger than the original forwards.