Why array implements IList?

Question

See the definition of System.Array class

public abstract class Array : IList, ...

Theoretically, I should be able to write this bit and be happy

int[] list = new int[] {};
IList iList = (IList)list;

I also should be able to call any method from the iList

 ilist.Add(1); //exception here

My question is not why I get an exception, but rather why Array implements IList?