I could have been more cynical. I could have said it's often a means of collusion to allow certain regions of the population to elevate their status within the wider group and take advantage of those who are not as well connected. Or simply for people to turn their surroundings into an echo chamber.
I don't think what I said was that ridiculous. For most people in the world friend groups are about precisely what I mentioned and anything beyond that is a luxury afforded to few.