The answer to 'why is my soffit missing shingles' is that the shingles on your soffit have likely become damaged or deteriorated over time. Soffits are the horizontal underside of the roof overhang, and they are exposed to the elements which can cause the shingles to wear down and detach. Common causes include weathering, water damage, and improper installation.
If you notice missing or damaged shingles on your soffit, it's important to address it promptly to prevent further damage to your roof and home. You may be able to replace the missing shingles yourself if it's a small area, but for larger or more complex issues, it's best to call in a professional roofing contractor to properly inspect and repair the soffit.