I like to think of them more as "ambassadors" - you see how cool a lion/monkey/snake/wolf/whatever is close up, and as a result you are more likely to support efforts to preserve them in the wild.
Is a point of view. We could even say the same to describe a spaceship. Other point of view could be that they are refugees in a safe zone. Would be naive to ignore than the same animals in the wild are being wipped at very fast and increasing pace. We could talk about the 3.000 orangutans killed each year in the wild for example.