The answer to 'why is my ridge vent missing shingles' is that the ridge vent shingles have likely become damaged or worn over time due to exposure to the elements. This can happen as the shingles on the ridge vent age and deteriorate, causing them to crack, curl, or fall off completely.
Some common causes include high winds, heavy rain or snow, and exposure to UV rays from the sun. When the ridge vent shingles are missing, it can allow water and pests to enter the attic, leading to further damage and potential leaks. To fix this, you may need to replace the damaged ridge vent shingles or consider installing a new ridge vent system.