why do people treat different people differently

Please name some example that people say or do different thing to different people and explain your viewpoint why they do like that?

nothing just because people are different!:)

In my view i think each person has different way to treat so as an example if you know someone very well, you will treat him or her very openly but if there is someone you dont know them well offcourse there would be much different in treating them.

because diferent culture and personnally

because different people we need do different method for them .

Thanks everybody for your valuable reply. Don't you think there are lots of  occasions that people treat people differently on purpose, I mean on their own selfish purpose, or only respect the people they need. That's really sucks, isn't it? sorry for my words…