I'd say it's a lot more basic than that; whatever we experience we consider "normal." Whatever happens to us is terribly important; when it happens to other people, not so much.

By the same logic (or lack of logic, really), whatever politics we have formed or inherited are "centrist," and anyone who believes otherwise is clearly a fringe nutjob.

It's just a matter of us, as human beings, being unable to have any perspective that is not our own.