Ever see a charity drive? Entertainers to pull in donations for helping the sick or needy? Zoos are basically that. They get a few injured or sick animals, or endangered species, make money on educating and viewing said animals, then use that money towards lobbying, research, and protection. Yes, some are stuck in a an enclosure, usually animals that would already be dead in the wild. However, they are helping other animals be rereleased in the wild, or protected by law, or understood so that the species can be saved in the future. Most in the US are nonprofit. Take Columbus for example. They not only have a zoo but a huge compound where the animals roam pastures in Ohio. Some of those animals were rehabilitated and returned to their home countries. Others are unable to survive without aid, and will chill out on that pasture until they eventually die. There are always greedy pricks who will abuse the nonprofit system (see also Columbus), but in the end they are providing a benefit to the world, and most people involved care for animals. So yeah, zoos aren't what they used to be, the small cages, barely fed, abused animals, sideshow entertainment spectacles. For one, laws in the US have become more strict, and two, humane societies and the WWF are very active in prosecuting and identifying bad faith actors. Oh and we could also get into how zoos are a great resource for helping veterinary medicine, zoological medicine, etc from within the US, rather than travel... I think you get it though.