Why are Labrador Retrievers generally unsuited to be guard dogs?

Their instinct is rarely to aggressively protect territory.

The Labrador Retriever's inherent friendliness is a defining characteristic that extends broadly to nearly everyone they encounter, including strangers. Because they often greet trusted friends and unfamiliar individuals, such as delivery drivers, with the same enthusiastic welcome, their temperament directly conflicts with the protective or deterrent instinct required of a guard dog. Their desire is to be near their human companions regardless of who those people are, meaning aggressive territorial defense is not an innate trait. This sociability, while a major benefit for families, disqualifies them from roles requiring suspicion or aggression toward unfamiliar people.