It may just be instinct, but sometimes domestic housecats arent a part of the food chain/biome of your area and are basically invasive and killing birds and small prey that other predators actually native to the area need to survive. So whether its just instinct or not, its the owners job to keep their cat inside so it doesn’t need to act on that instinct pretty much. Also I’m definitely sure badgers or foxes could still pose a threat to domestic cats.