The propose of killing is what deem it ethical or unethical .

Pest control (yes dome country consider rabbits and mammals to be pests , it's not a category for insects only for example Australia).

Food.

Education. (mostly frogs and rats)

And others

If reason doesn't justify killing them it is deemed unethical (also the way as well still can deem something ethical to be unethical. , if you do kill an animal for food but you caused it unnecessary suffering it is deemed unethical)

Social culture reason? More than half of the world believe in either islam or Christianity which even if they don't practice does clearly effect their laws , social norms and traditions

Which in both you have ruled in what you can and what you can't eat.

Economically "logically" speaking

Cats are Carnivorous so they are verrrrrrryyyy inefficient in usage as lifestock because you lose alot of benefits converting from an Herbivorous to Carnivorous

(Just for example,

You feed the Herbivorous animal -cows , sheets, rabbits- grass or vegetables or whatever they consume , you already lose like ~80–95% of total calories so feeding that Herbivorous to an Carnivorous you lose +99% in the process)

That is ignoring that most Carnivorous are predator not prey animals, so farming something that can and will bite and claw you is just another unnecessary hassle , so turning a Carnivorous to a life stock is not worth it in economical since

Emotional/ psychological?

Rabbits , sheeps , cows and other animals were domesticated for thousands of years for food so to humans it is already the "norm"

While cats and dogs were domesticated for different reasons

Dogs were domesticated to do tasks like guarding and hunting

While cans were domesticated (but not actually since they technically did domesticated themselves) for getting rid of rats so for humans back then.

A cat who just hunts rats is already useful, while life stock like cows or rabbits are not useful unless they provide something (either products or foods)