Why should the outer jacket of coaxial cable be resistant to ultraviolet light?

Coaxial cables used outdoors for antennas are constantly exposed to the sun. The ultraviolet (UV) radiation in sunlight is notoriously harsh on standard plastics and vinyls, causing them to dry out, become brittle, and crack open over time. Once the protective outer jacket develops cracks, the cable is no longer weatherproof. Rain, dew, and humidity will seep into the coax, which inevitably compromises the dielectric and corrodes the metallic shield. Specifying a UV-resistant outer jacket ensures the physical integrity of the cable remains intact to keep water out.