That is a good question. I think it is because cats have paws and sensitive noses and humans have hands. If cats had hands they couldn't run around fast doing all the things they need to do, such as guarding the house from vermins.
She is always trying to 'correct' me. I thought there was more than one vermin.
And when they catch a vermin, they tear it with their sharp teethypegs.
What are hands useful for? Hands are good for opening packets of cat food.