On minute 1:35 you create an edge in the middle of the top part of the eye. Why not just get rid of this edge and fill the eye with bigger quads? This will lead to less vertices/edges. Could you explain it please?
So, it is used for creating a bit more of control over that segment. I thought it was because you prefered a grid of quads instead of a smaller number of bigger quads. This make sense now.