They are simply the best sun lens there is. Eliminating reflected glare gives all sportsmen an advantage they can see. Fishermen can see the action beneath the water's surface. Hunters can see into the brush and trees better now that the glare from the leaves is gone. Skiers can gauge the depth of the moguls and differentiate contrast in the shadows.
Golfers can pick up the ball in flight quicker and read greens more accurately.
Eliminating the glare benefits all outdoor activity whether it be fishing, boating, driving, hiking, biking, playing sports, or just laying around the pool.