The answer to 'why is my soffit missing shingles' is that the soffit shingles have likely become damaged or worn over time, causing them to fall off. Soffits are the horizontal underside of the roof overhang, and they are exposed to the elements which can cause the shingles to deteriorate. Common causes include weather exposure, age, and improper installation.
Symptoms of missing soffit shingles may include visible gaps or holes in the soffit, water damage, or even pests entering the attic space. To fix this issue, you'll need to replace the missing shingles. This is typically a DIY-friendly repair, but if the underlying structure is damaged, it's best to call a professional roofing contractor to inspect and make the necessary repairs.