The proverb uses simple observations to comment on causation. Wealth in those days, moreso than today, was characterized among other things by cattle and farm produce. Hence it would be common for people to admire a kraal or chaff (representing grain seed) but not fully appreciating the work of the farmer or cattle breeder to generate sufficient farm produce or raise cattle successfully. These products do not come to being without the strategic planning, relentless labour and forward thinking. What is further interesting in this imagery is the futuristic planning since chaff would be for future planting while the kraal is testament to more cattle coming - an element that would amount to savings in the contemporary sense. Hence it is not sufficient to admire the product but one must also appreciate the planning and future thinking. The lesson from our elders is both on causation as it is on planning and saving.
The proverb is used as a comment on causation to attest that there is effort exerted behind noble outcomes. It is also used to encourage and caution people to not only admire the product but realize that if they like the product they must be prepared to commit to the work behind the product including the necessary futuristic planning.