What makes us feel we need to share our opinions with communities and the world?

People put signs in their yards stating who they will vote for, people go online to debate/argue about the same.
Politics, religion and just about anything under the sun... people will argue about it all and even resort to be rude, insulting, etc.... and yet, it never makes a real difference in anyone's life.

Why do we feel anyone really cares about our opinions? (unless they are like minded)