is a zoo useful?

Now zoo's only purpose isn't offer a new kind of entertainment to public and make money in the process.Scientist is begin to be curious about the animals'sanatomy,thier diseases,and their habits,althouth it is nearly impossible to judge their normal behavior under the conditions of their captivity.

I think more than zoos, wildlife sanctuaries are better for the animals. I feel instead of caging animals in a zoo, we should let them roam free in some sanctuary. It would be good both for the visitors as well as the animals.