Why isn't the highest point on a hill represented by a contour line?

The highest point of a hill (or mountain) is a single point.
a single point can only be precisely marked with a dot. 
putting on a contour line is impossible  on a single point because the contour line is created after multiple points that have the same hight are marked, and after that, all of those points are connected with a line that creates a closed area. so the highest point, as said above, is a single point, there are no other points with the same height, so the only possible way for it to be marked is with a dot, and there is no possibility for a contour line.

The "highest" point is a single point. 
there can't be more than one "highest" point.
it's not possible for every point on a line to be the "highest" one.