Why do visa officers suspect that people who only apply for short-term visas have immigration tendencies?

Visa officers never doubt people who apply for immigration through legitimate channels, because immigration is allowed. The immigrants they usually refer to are people who apply for short-term visas and stay without returning. In fact, they are illegal immigrants (commonly known as illegal immigrants). : run away), people who run away usually disappear after arriving in the destination country. This is a headache for governments of various countries.