I am friends with someone who works in health education and we have talked about this. She thinks that anyone who is not very depressed wants to live a long time, and all they need is to know how to do this.
I think a lot of people actually do not want to live a long time. Even for many physically healthy people very old age can be a harsh time. Many people are very lonely, constant bereavements is an ordinary part of the territory, and seeing loved ones die from painful illnesses is tough.