I think people stay in touch out of a sense of guilt or wanting security. You feel you should love your parents because they gave birth to you and took care of you for many years. But just because someone gave birth for you and even took care of you doesn't mean you two are psychologically compatible and comfortable around each other.
I think security is a motive for staying in touch. If you ever got in a truly troubling situation, your family might be among the only ones who would be willing to bail you out.