As any student of economics can tell you, specialization plays a huge role in helping to grow a country's economy. That's true, too, of human evolution. As humans evolved and began inventing new technologies, we moved beyond being solely hunters and gatherers, and began to specialize in particular crafts.
Once we began practicing a division of labor, the way in which we looked for work eventually changed too. Of course, job hunting as we know it, at least in the Western world, is a relatively new phenomenon. It coincided with the dawning of the industrial Revolution, a little more than 200 years ago.