There is only one reason for placing one's self above another: Desire for Supremacy.
There are several reasons that humans desire supremacy, but only a few basic reasons, and they are all based in Group Dynamics. Without a group, there is no "Higher" or "Lower", so those who desire Supremacy also desire belonging, and fear being diminished or cast out.
Some basic reasons are:
~Fear of being seen as "Lesser", and associated with those who are seen as "Lesser", and consequently being denied privileges, attention, and resources (because one has seen this happen and knows it to be a real threat).
~Craving to be associated with, seen as, and thought of as one of those who are Powerful, and therefore automatically cared for and liked by others.
~Fear of humiliation; if one's "Station" is at the top, then no other is allowed to point out their mistakes, failings, or flaws.
~Fear of being judged, ridiculed, or ostracized.
~Fear of being seen as weaker, less knowledgeable, less wise, less powerful, and less deserving, therefore being cast out.
Humans who crave Supremacy (it's not a rare occurrence) will use absolutely anything to "prove" why they, personally, naturally "deserve" it.
Some extremely common reasons that humans have used to try to claim natural Supremacy are:
~Certificates of education
Emotionally and mentally healthy human groups do not play games of status, power and control, and are focused on the genuine well-being of all members of the group in body, mind, and spirit. Therefore the desire for Supremacy in such groups is minimal because there is no fear of denial of basic needs or rights, and no fear of favoritism, exclusion, or unfairness. Adults regularly mentor youth in a calm and caring manner, and members of the group exchange accurate, positive feedback on a continual basis. All members are treated as real members of the group. It is the "norm" for all members to be heard by all other members, and it is very abnormal for anyone to be left out, talked over, insulted, or shushed.
The only "ostracism" that occurs, if it ever does, is when a member would purposely dominate and harm (physically, which includes sexually and mentally) another member (ANY other member). The occurrence of violent/criminal behavior within such a group is rare because there is continual healthy interaction, guidance, mentoring, caring, respect, and accurate, polite, healthy feedback., from all members, toward all members.
This behavior is learned because it is modeled, and it is modeled because it is comprehended.
The strength of such a group is far beyond groups who are full of power struggles, envy, self-righteousness, hatred, and domination behavior.
This strong and healthy dynamic does NOT begin on a governmental level, but on the most basic and personal level. It begins in the home, in intimate relationships, in the family, in the neighborhood, and in the community.