The primary purpose of phasing out ozone-depleting substances is to protect the ozone layer, which shields the Earth from harmful ultraviolet (UV) radiation. By reducing these substances, such as chlorofluorocarbons (CFCs), we mitigate the depletion of the ozone layer, preventing increased rates of skin cancer, cataracts, and other health issues. This phase-out also contributes to the overall improvement of environmental health, supporting climate stability and the preservation of ecosystems.