Kangaroo Sight

Why do Kangaroos sit still? This is my guess from observations.
It is a defense method. Their eye sight is poor, so they cannot see clearly until an object moves. So they assume everyone else is the same.
So if they are in flight, they travel fast, in a straight line.
But if they are just going for a walk, they wander left and right, in a snake-like path.
When I stand still and call them for breakfast, they just stand there confused. Immediately I move, in any direction, they know banana is on the menu and come directly.
PS: They are more intelligent than any dog or cat I have ever met, more easily befriended and never disgraced themselves in the house.