What is a tribe -
As per Merriam Website a tribe can be any of the these
a social group composed chiefly of numerous families, clans, or generations having a shared ancestry and language or : a political division of the Roman people originally representing one of the three original tribes of ancient Rome or : a group of persons having a common character, occupation, or interest or : a category of taxonomic classification ranking below a subfamily or : a natural group irrespective of taxonomic rank
Real world has tribes. Artificial world also has tribes. I believe companies, nations, communities, and religions are all forms of tribes. So, what’s the need of a tribe?
Animals need a tribe because being in a tribe reduces the risk in a dangerous situation. You have many eyes, many hands in a tribe and so you can survive most of the dangers. Tribes also increase the chances of success, provided a tribe has more advantage than other tribes. Some tribes can be more powerful than the others. When some people don’t feel safe in this tribe, they move out to other tribes where they feel more safe.
Some tribe members can also dare to start a new tribe - ego, advantage, stupidity, etc are some of the reasons why new tribes would be formed.
A special note - Some people are very much interested in becoming head of the tribe or want to end up closer to the head title of the tribe. They play to reach there but in the end, they fail to realize, everything is virtual.