We use these same yin/yang principles of opposing concepts in our everyday life. This ability to conceptualize and understand different points of view (of ideas, values, lifestyles, or choices, etc) helps us define and clarify our own beliefs and ideas, or what we want, what we want to be, or what we even know and understand.
For example, how often do you find yourself trying to decide what you want to do and you can't quite clarify what you want. This can happen when you are faced with any choice. You may not know what you want for dinner, or what music to listen to, or what movie to watch. You just aren't sure, so you start to think about or even list the things you DON'T want. Those things are clearer to you. Knowing what you DON'T want helps you narrow the field to help you identify what you DO want. When this happens, you are using the yin/yang concept to help sift through and clarify your feelings, ideas, and even next steps.
This is the same process that is happening today in the USA election process. There are many Republican candidates running, but one person is standing out; Donald Trump. His openness and off-the-cuff remarks are, for some people, helping them to clarify their pent up anger and unexpressed or unsupported frustrations. For others, Trump is helping them clarify and articulate who they are NOT and what they don't want America to represent.
There is a purpose and reason for having this type of opposing processes. It provides an open forum of exposure to help us clarify our beliefs, ideas, and next steps. It helps us decide who we think we are or who we want to become.