Why do we care about endangered animals?

I was wondering why we care about endagered animals. Is it only the ones that are endangered by human actions or all of them? Can I please hear from people who think it's okay to eat animals and hunt them for sport (like most Americans do). Why is it okay to go out and shoot a quail, but it's not okay to build a house where some tree frog may be living? Why does it matter that there are tons of quails but maybe only a couple hundred of those tree frogs?