This is because the replenishment of these waters is only due to precipitation. For example, if it rained, he still needs to be able to seep deep into the soil in order to replenish the inter reservoir. To do this, he must first moisten all this thickness of the earth, “water” all the plants, all the inhabitants of the soil, round the waterproof layers. And only after all these adventures, the remnants of the water will be able to join the accumulating waters.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.