It is arguably true that the only time an average person engage in thinking is when he is confronted with a problem.

In defence of an average person...
I think this is so because, not all problems are predicatable and they may hit the average person in different folds. So they wait for problems to come before searching for a solution.

However, if you're not thinking all the time, you're dead.

I like the well selected quotes, especially the one by Jean Jacques Rousseau which decribes the average person.