There are many reasons for rehabilitating wildlife. They are personal, professional and organizational, but not always easy to explain.
One of the reasons was said best by Loren Eiseley in "The Star Thrower". Here's an excerpt from an adaptation by Joel Barker:
Once upon a time, there was a wise man, much like Eiseley himself, who used to go to the ocean to do his writing. He had a habit of walking on the beach before he began his work. One day he was walking along the shore. As he looked down the beach, he saw a human figure moving like a dancer. He smiled to himself to think of someone who would dance to the day. So he began to walk faster to catch up. As he got closer, he saw that it was a young man and the young man wasn't dancing, but instead he was reaching down to the shore, picking up something and very gently throwing it into the ocean.
As he got closer, he called out, "Good morning! What are you doing?" The young man paused, looked up and replied "Throwing starfish into the ocean."
"I guess I should have asked, Why are you throwing starfish into the ocean?"
"The sun is up and the tide is going out. And if I don't throw them in they'll die."
"But young man, don't you realize that there are miles and miles of beach and starfish all along it. You can't possibly make a difference!"
The young man listened politely. Then bent down, picked up another starfish and threw it into the sea, past the breaking waves. "It made a difference for that one!"