A)
Because super indicates the lower bounding class of a generic element. So, List could represent List or List.
B)
Because the compiler doesn't know what the actual type of List is.
Your adding an object with shapeSuper.add(new Object()); but the compiler only knows that the the generic type of List is a super type of Shape but doesn't know exactly witch one it is.
In your example, List could really be List forcing the compiler to disallow the shapeSuper.add(new Object()); operation.
Remember, Generics are not covariant.
