its because animals are generally considered innocent beings in which we largely control the lives of and therefore are stewards to them, its the reason why people are outraged over the environment as well and the lie of global warming, its something we live with, care for, take from it. why people dont care as much for humans is because of our sinful nature, and because of the constant propaganda launched at us we have developed as a whole, a hatred for ourselves which also means a hatred for others. in animals we can see qualities of humanity but presented in a more simpler, innocent form, like a child you can say. even in something as biologically simple as a lobster, you can see that every one of them is different. you can even see different behaviors and personalities between them. they can even interact with you if you are around them long enough as they recognize you, and not in a defensive or hostile way either. this can also be seen in people's treatment of children, they see them as themselves but unblotched by the world. humanity's emotion and morals have not completely gone away however, as stories of oppression in other countries and stories manipulated in a way have gotten us spun up to do what the deepstate wants. but they hate their are taught that their own country, race, history is evil and they do not care for themselves.

sorry for the lengthy answer.