There are many theories that arise as to how office politics exist. One such explanation that experts give us is the Prisoner's Dilemma.It was called such as a comparison to two prisoners who will given the chance to reduce their sentences if they incriminate each other.
What does this have to do with office politics? In simple English, there is no team work because everybody is pushing his/her own interests.
Link: Prisoner's Dilemma - Science behind Office Politics