Animal Sidekicks

The most successful animated films all have protagonists with some kind of animal sidekick. The most notable studios, Disney and Studio Ghibli, have films that almost always have animal sidekicks, especially if the main character is a heroine. Disney's Tangled has a chameleon companion, and Miyazaki's Kiki's Delivery Service has a black cat as the trusty friend. Pretty much almost all of Miyazaki's works has an animal sidekick. What is the importance of including an animal sidekick? Is it because Miyazaki's films send the message of being one with nature that he finds it necessary for the protagonists to be always physically close to nature's creatures? Or is it simple because audiences react well to the cuteness and appeal of animal sidekicks?