When the sole purpose becomes realizing the self (and mentally leaving everything you are not) and in the moments when you are at utter peace, you don't search for what is the purpose of mind or anyone else.

Everything in life is pushing us to realize our true self, whether we are able to discern it or not. Mind is a beautiful tool given for survival. But somewhere mind became ego when we think we are the thoughts, beliefs and emotions. If conscious, it becomes a path to the self growth.