Many players just love to place the ball right at the upper corner of the goal, but I have found out, that the players do not think about the chances for a goal with these shots.

If we take out the goalkeepers ability to take high and low shots and instead look at the chance for a goal, you might look at it in this way:

A high shot may:
 - be inside the goal frame = chance for a goal
 - pass over the goal frame = no chance for a goal
 - pass the outside of the goal = no chance for a goal

A low shot may:
 - hit inside the goal frame = chance for a goal
 - hit the floor and bounce into the goal frame = chance for a goal
 - pass the outside of the goal = no chance for a goal

This mean that you have an extra chance for goal if you shoot low. In stead of passing over the goal frame, a low shot may pass "under the goal frame" and still give a chance for a goal.

Worth giving a thought.