In a perfect society, no one would harm anyone else. That means no one would harm you. Human beings entered into “social contracts” to form governments. We trade freedoms for security. The most basic level of this is: “I won’t kill you if you won’t kill me.” It’s all about our own safety.
So, one could argue that humans formed societies to benefit themselves. Then, if a society is based on selfish goals, shouldn’t a perfect society be the result of the ultimate selfishness? Without perfection, there is uncertainty. Anyone can get you. Only when everyone is truly happy, will no one harm you.
There’s truly a great irony in this, if it indeed stems from selfishness. It is that in order for you to be perfectly happy, you must make everyone else perfectly happy. Yet, it is our own selfishness that prevents us from making everyone else happy. Quite the dilemma.