It’s worth pointing out that some (many?) animals are in zoos because — for one reason or another — circumstances are such that they are otherwise incapable of

It’s worth pointing out that some (many?) animals are in zoos because — for one reason or another — circumstances are such that they are otherwise incapable of surving in the wild. You’re right that enclosure size is mostly determined by business concerns rather than animal satisfaction. Practically speaking, however, the enclosures can rarely be large enough to completely suit an animal’s needs.