Agree, CrazyTalk - I think dogs are a worse threat. Nevertheless I've known cats that killed chickens. So in my own life experience - cats will kill chickens if they have the chance. They are opportunistic and will kill (usually) young chickens if they can. And again - as I said before - this doesn't mean that all cats kill chickens, or that they always kill chickens - but they will, if they think it will work out well for them. And again I've personally owned a cat that regularly brought down full-grown cottontail rabbits.
I guess I think of it like coyotes. We have a ton of coyotes here but they spend all their time digging up pocket gophers and prairie dogs. Every time I've lost an animal people want to blame the coyotes; every time, it's been domestic dogs. But just because these particular coyotes don't kill chickens, it doesn't mean that coyotes don't kill chickens; they sure will, if the circumstance is right.