We can't even handle stray/unwanted cats and dogs, even though that's a serious problem we encounter every day. Zoos and aquariums do a lot of work with research and rehabilitation of animals. Cheetahs and white rhinos would have gone extinct by now if it weren't for zoos (though white rhinos are down to two females left in the world).

It's really shitty how animals have suffered dire consequences for human behavior. And humans won't even change the system to help our own pets, let alone our own species. Zoos charging admission for people to see something educational for the animals' benefit isn't a problem in the grand scheme of things.

Note: this only applies to accredited zoos and aquariums. There are non-research/rehabilitation facilities run strictly for profit, though they're becoming rarer as more governments around the world pass laws against them.