It makes a big difference if the wind is blowing 30 miles per hour
from the North, from the South, from the East, from the West, or
from the Southeast, etc.
In order to fly the plane in the direction that he actually wants to go, the
pilot needs to handle every possible wind direction in a different way.
If he only knows that the air he's in is moving over the ground at 30 miles
per hour, he would have no way to make the required correction, and the
airplane would get blown way off-course.
