Five reasons to keep your cat inside
Large birds might kill small cats.
Great horned owls also focus on small mammals and birds, but they have the most diverse diet of any North American raptor, including larger animals like skunks, ducks and even other raptors. They don't pose a serious threat to pets overall, although they have been known to attack house cats and chickens left outside overnight. Even then, however, they rarely just whisk away such large prey, as wildlife rehabilitator Steve Hall writes in the Adirondack Almanac, instead killing it on the ground and tearing it into smaller pieces first. Fortunately, this risk can be reduced by keeping cats inside at night and letting chickens sleep in a predator-proof coop.
Red-tailed hawks mainly eat small mammals like rodents and rabbits, plus birds and snakes, and aren't considered a threat to most pets. That said, some larger red-tailed hawks may be able to carry prey weighing 5 pounds (2 kg), according to the Cornell Lab of Ornithology, which could include not just puppies and kittens, but also some adult cats and dogs from small breeds.
https://www.treehugger.com/how-much-weight-can-hawk-carry-4868712
Large birds might take a swipe at a very tiny dog. If you have one, be careful and use common sense. If you have a cat, keep it inside.
“All birds of prey are protected by state and federal law,” says Eileen Wicker. “If you harm one or threaten one in any manner, you are subject to a fine and prison term. Appreciate their beauty, and their value to our earth.”
https://www.10000birds.com/can-a-hawk-carry-off-your-12-pound-pet.htm
Cats can get a skin disease called “warbles.”
The only way to prevent warbles in cats is to keep your cat from investigating rabbit or rodent burrows. If she roams freely outside, you are unlikely to stop her from poking into burrows.
So the only prevention method is keeping your cat indoors, or allowing her supervised outdoor time in an enclosed area where there are no burrows or through leash walking activities.
https://www.greatpetcare.com/cat-health/warbles-in-cats/
Do you need three more reasons to keep cats indoors?
Rabies
Feline Leukemia
and more reasons are here. (https://catbehaviorassociates.com/)
See Pam Johnson's "10 Ways to Keep Your Cat Happy"