Why?

Why is it so hard to treat others the way they want to be treated?  Why is it ok for an adult to act like a total child, yelling, hollering, slamming doors, etc. when they are mad or something didn't go their way?  How is it that one person can create such a hostile environment?  Why after throwing the fit and creating so much tension in the room, the person creating that tension then wants to be best friends?  (Not literally)  Why is it so hard to treat someone like you want to be treated?  Why is it so difficult to tell someone that they are appreciated?  Why is it so hard to encourage someone, whether vocally or through a note or an email?  Why can some people only point out the bad in a situation or in a person, yet never even acknowledge the good?  How is it, when confronted with some of these questions, a person says "yes, I agree" and yet they make absolutely NO effort to change things?

(And to those who might wonder-this is NOT in reference in any way, to Steve)