Oh, there are many reasons for that and I wonder if anyone understand people! I suspect most people have problem understanding themselves!
Humans are so complex and our behaviour depends on many parameters like heritage, environment, experiences we have done during our life, the conclusions we draw from our experiences, how we live, people we meet, just to mention a few. I am very interested in peoples behaviour and I spend time trying to find out why people behave like they do and why!
I have always had jobs that include working with people and I have met all sorts of people both from my work in health care and in my present work as a environment and health inspector. But despite my experience working with people and from my personal life I still get very surprised over peoples behaviour now and then.
What I really would want is to see more genuine people that don't play roles or have a hidden agenda!