Ancestor worship and funeral etiquette are very important in China culture. Traditionally, ancestors were regarded as guardians and guides of families, so they attached great importance to respect and belief in their tombstones. If grandpa's tombstone is covered, it may affect the feng shui of the family, the fortune of future generations and the rest of ancestors.
As a place of sacrifice and commemoration, the cleanliness and visibility of the cemetery are also very important. If the tombstone is covered and nobody cares about it, it may make people feel disrespectful to their ancestors, disrespectful or lacking humanistic care. Of course, in modern society, many people no longer attach so much importance to these traditional beliefs and customs, so tombstones may have no influence on them. Solemnly declare: the answer is for reference only, please don't be blindly superstitious.