AS3 Whats the purpose of having abstract/interface class?

hi guys,

whats the purpose of having to have an extra class such as abstract class in Flash
where the methods has no implementation,
but the subclasses declare those implementations.

Isn’t it a hassle?

The advantage of having the methods declared in subclass than the superclass is
that it would not affect the other subclasses when there are certain changes.

That makes me wonder, isn’t it better not to extend(inherit) empty methods but
directly create a class as its own? unless there is something that the child could use from parent.

Anyone could give me examples of how applicable using abstract classes/interfaces?