The main reason why you cannot keep multiple cats at home is because cats live in places where the breeding density is too high, and they are prone to emotional stress and can easily transmit viruses to each other. Cats, unlike dogs, are not animals that live in groups. Keeping too many cats in the same space will result in too high a density. This will make cats' lives stressful, and it is also very easy for cats to transmit viruses to each other, causing inflammation of the cat's lower urinary tract and behavioral abnormalities caused by psychological stress.