The answer to 'shrub thin grass' is that thinning grass around shrubs is a common landscaping issue. Shrubs can compete with surrounding grass for nutrients, water, and sunlight, causing the grass to thin out or die. Symptoms include bare or patchy areas around the base of the shrub.
To fix this, you can try pruning back the shrub to reduce its size and competition with the grass. You can also aerate the soil around the shrub and overseed the thinning grass areas. If the problem persists, you may need to consider replacing the grass with a more shade-tolerant groundcover that can thrive in the shrub's conditions.