Why can we only expand the access modifier visibility of the overridden method?

Question

Java

This refers to cases similar to those of overriding the clone() method of the Cloneable interface.
It seems to be not quite a beginner, but for some reason I can not collect the final and well-formulated goal. I understand that here we are talking about polymorphism and that when calling in an object whose class overrides such a method, the same overridden method is called by us, and not the parent method. Please dot all the i's :)