The concept of a tiger is an important part of human culture, and it would be a pity if nobody could see a real one, but they breed in captivity, so people can see them in zoos. It's easy to romanticize the idea of "wild tigers" when they live far from you, and you're at no risk of one eating you or your livestock. Humans killed most wild tigers for good reason.
Human beings are not supposed to be apex predators but we have taken over that role without embracing the intricacies of the responsibilities involved with it.
To all the downvoters, what is the maximum number of humans eaten by tigers per year you'd be willing to accept in exchange for allowing them to roam free?
Don't try to build such a general argument on such marginal premises. Humans kill far more humans that Tigers ever have. Tigers are simply not a serious threat to us.
All of them.
Certainly there are bad zoos, and I support legislation to enforce high standards of animal welfare, but the only animal I am aware of that is absolutely unsuited to captivity is the killer whale (which IMO might be smart enough to have some philosophical understanding of abstract freedom).
From Wikipedia: "The most comprehensive study of deaths due to tiger attacks estimates that at least 373,000 people died due to tiger attacks between 1800 and 2009, the majority of these attacks occurring in South and Southeast Asia.[1] Over the last five centuries, an estimated 1 million people have been eaten by tigers.[2]"
https://en.wikipedia.org/wiki/Tiger_attack