Although cats have natural hunting instinct, they still find it easier to scavenge for leftovers than to hunt for mice and rats.

Cats need to practice their hunting techniques so they can be effective hunters.

Cats (as kittens) need to be taught that mice and rats are food. Otherwise they will just treat them as playthings. This is generally the job of the kitten's mother. But if the kittens were adopted by people, they will lose this valuable training in their upbringing.