Why does downcycling occur when materials are recycled?

Downcycling occurs when materials are recycled into products of lower quality or reduced functionality, which is the essence of option C. This phenomenon often arises due to the degradation of the material's properties during the recycling process. For example, when plastics are recycled, they may lose strength, durability, or other desirable qualities, leading them to be repurposed into lower-grade products.

In contrast, the other choices present concepts that do not align with the realities of downcycling. For instance, enhancing the quality of materials through recycling (as in option A) is not accurate in the context of downcycling, as the opposite is true: the quality is usually diminished. Additionally, if the recycling process maintained the original quality of materials (as implied in option B), we would not refer to it as downcycling but rather as recycling with high fidelity. Lastly, while the process creates new materials from old ones (stated in option D), this statement is overly broad and does not capture the specific aspect of downcycling, which is the reduction in quality of the material produced.