Friendship arises out of shared goals, family, history. For most of time, folks tended to be closely related and they stayed in their local town or village their whole lives. It is only in this modern age that people are so unglued from the natural that they attach something supernatural to friendship.
I noticed this in, of all things, The Guardians of the Galaxy. It was a great bit of cheesy fun, and then there in the middle of it all is the old dorky ode to friendship. Hey, these guys are together because they've got a common enemy, terrible family histories, and a general tendency to flout the law, but lets forget about all that and have the sort of ode to friendship the scrawny nerd types think is true.
The reality is that the inordinate fondness of friendship leads to fear, and the fearful are easily manipulated. They are more likely to ignore injustices and even the loss of one friend in the face of the possibility that taking a moral stand against that injustice will lead to exclusion from the group. In many cases, you find the weak doing this to themselves in order to have some pale imitation of what they presume friendship to be.