The answer to 'why is my drip edge worn out' is that drip edges can become worn out over time due to exposure to the elements and general wear and tear. Common causes include heavy rain, strong winds, and freeze-thaw cycles that can cause the metal to corrode or the sealant to degrade. Symptoms of a worn out drip edge include peeling, cracking, or rusting along the edge of the roof.
The solution is typically to replace the worn out drip edge. This is a relatively straightforward DIY project for handy homeowners, but it's important to take safety precautions when working on the roof. For more extensive damage or if you're not comfortable doing it yourself, it's best to call in a professional roofing contractor to inspect and replace the drip edge properly.