This is at least in part due to the popularity of these animals as household pets. But the most important reason is that humans develop allergy to these animals more readily than to most other pets.
Cat allergy is by far the commonest allergy to pet animals.
Although they carry many potential allergens, the most important of these are found in cat saliva. Since they constantly groom themselves, these allergens are deposited on the fur and transferred to carpets, furniture, bed linen, etc. Even in minute amounts these allergens can have devastating effects on allergy-prone individuals. And even after these animals are removed from the house, significant amounts of the allergens linger in the house for several months. The only sensible solution for cal allergy is removing the animal from the house and thoroughly cleaning the floor, walls, furniture and so on.