In every situation, the most natural strategy is to maximize personal gains. That's how natural selection works. But when people don't act like that, it means there must be some opposing force, normally one that benefits society. There is a lot to learn here, in fields as diverse as biology, economics, computing, and of course, games.
That is how I understood GP's comment.
The iterated prisoner's dilemma begs to differ.
There are many many situations where cooperation is both natural and optimal.
i.e., there is something in it for them. It doesn't have to be a tangible thing, it could be a simple as self-satisfaction.
It does point to the advantages of not defecting on players who cooperate.
The best you can do if you have no idea what strategies are in place is to employ Tit For Tat (I think?) as it's optimal under the largest number of conditions but not all the time.
I think it depends upon the person who is asking. The average person asking it comes from a different perspective than someone who studies game theory and human nature asking the question.