Why does rose Mary believe she’s doing animals a favor by not allowing them to become dependent on Humans?

From the text:

We couldn't afford pet food, so the animals had to eat our leftovers, and there usually wasn't much. "If they don't like it, they can leave," said Mom. "Just because they live here doesn't mean I'm going to wait on them hand and foot." Mom told us that we were actually doing the animals a favor by not allowing them to become dependent on us. That way, if we ever had to leave, they'd be able to get by on their own. Mom liked to encourage self­sufficiency in all living creatures.