Kali is a highly misunderstood goddess. She is often misinterpreted as a violent mother. Her wrathful form represents the destruction of illusion of self, the great state of liberation and understanding of emptiness.
We need to come to a clean slate within before we can create anything truly divine. This is why we need Kali. She is also worshiped in India for the purposes of protection, enlightenment and help on a spiritual path.