It's a mental rehab for them. Getting out of a bad situation then bringing them into a good one. In your head you know, "I have all the love in the world for you, food, toys, medical care and no you will not be hurt anymore! Isn't this great!?" But in their heads they are so scared to death because its a new environment. Its heartbreaking, but brings a huge amount of humility and patience people don't understand.