While both very important, they are different. Animals being slaughtered are completely and utterly powerless. They cannot do anything to get themselves out of that situation. They need a voice for them.
People working for companies that severely underpay them and contribute to local poverty have a different situation. They can feasibly, though it is very difficult, get themselves out and to a better life.
Before someone misconstrues this and gets offended that I’m defending abusive labor practices, I think fighting for the rights of both humans and animals is very important. But again, it’s different because animals born into these slaughterhouses are 100% powerless without help