The productivity of a worker is not entirely within his control. In almost any occupation, it depends on factors that supplement the work. These include equipment quality, management, and colleagues.
In developing countries, the lack of modern highways and efficient transport increases the cost of a product. This concomitantly diminishes the value of the labour that went into producing it. For an analogy, a careful pitcher can minimise a world-class batter’s impact on a game by ensuring he has fewer opportunities to hit home runs.