Why do people keep animals in zoos and parks? where do animals have more space for living? where do animals have a better place to live and why?

People keep animals in the zoo or parks because they want to preserve some species that are under extinction or because they want to make a place where people can see animals that they can`t see in ordinary life. 
Animals have more space in the park or when they are living free. I think that better space to live for the animals is freedom, but we must preserve zoos and parks in any case.