Christine tossed out some snacks, they try to keep the cheetahs conditioned to come over when they see the keepers, and rewarding them is the easiest way to do that. This way they don't have to do anything fancy to get them medication. Despite not being particularly large, it would require anesthesia anytime they had to get their hands on one. This is bad, it's not very easy to judge the weight of a cat without being able to touch it or get very close, and cats tend to shake off anesthesia anyway.