Kittens are usually quite friendly and playful with other cats and their human family. They participate in family functions. We perpetuate these kitten qualities through ongoing care and play with them. The kitten matures physically, but mentally retains kitten-like behavior. Cats that retain kitten-like behavior adjust to and probably prefer group living.
Some people describe cats as untrainable.
Again that's from the human perspective. Of course a cat is trainable. What makes a cat appear untrainable is the fact that it will perform what it was trained to do on the basis of whether or not it wants to do it. Because the cat is not a pack animal, there is no inherent need or desire for the cat to comply with anyone's wishes but its own. We humans have a difficult time accepting this because we relate as pack animals.