If anyone here truly knows the answer to that question, they would be answering a question that has been asked and unanswered down through the ages. The best one can do is give an educated guess. When you talk of difference, you talk of change. Change is a condition that man abhors. Change is unfamiliar territory and means that the status quo man knows to be normal and correct was, in fact, flawed. There is a better way, after all. When difference or change is involved, it requires trust that the difference (or change) is going to be an improvement. This means that the person or organization that implements the change (difference) mist be trusted. This is where the fear comes into play. Can the change/difference maker be trusted? Has he (or the organization) shown himself/itself to be trustworthy in the past? Fear of change and fear of something different in ones life can be an all consuming fear. If the proposed change or difference goes in defiance of what has worked in the past, it goes against man's calm acceptance of the status quo. He becomes fearful and even defiant when he is pushed to accept a different method of doing things or a change in the norm he has has known. In essence, I think the answer to your question is - FEAR. Humans are afraid of difference and change.