One of the little things that's quite clear from even a brief examination of human nature:
Regular exercise can extend life, but 90% of humanity would rather die than submit to a daily workout. ... Last week, an international conference in Brazil heard from scientist Professor Frank Booth, who gave a talk about how the lack of physical activity can be shown to significantly reduce lifespan. The current USA guidelines for physical activity are 30 minutes a day for somebody over 20 years old, but he reported that over 90% of people do not do this amount and are shortening their life as a result.
Human psychology is hardwired to discount future rewards, a thing called time preference. The future reward that is an increased chance of being alive in sixty years tends to have a lower value for most people than, say, substituting a video game or nap for exercise right now. Sad but true. So there is more gaming, less exercise, and shorter lives on balance. Time preference is pretty good in the environment in which we evolved, but becomes increasingly less helpful the more civilized and technologically enabled that environment becomes.
So equally, if low-cost life-extending therapies existed - along the lines of the rejuvenation biotechnologies proposed by the SENS Foundation - and not using them was viewed as something akin to failing to brush your teeth, then many of the same people who skip exercise would make the effort to head to the clinic every few years and thereby live longer. Social pressure also enters into value judgments, a cost to be measured alongside others. It is entirely possible that people of future years will be using longevity medicine for reasons that have little to do with their own longevity; after all, they will still be operating with the same time preference as we do. Being alive sixty years in the future has a small value for the average human being.
This is one of the reasons why so very many people make themselves more sick than they have to be, and die younger than they might have. They didn't take care of themselves, despite knowing that they could do a better job. Separately, but a part of the same pattern of psychology, today there exists the realistic prospect of building actual, working means of rejuvenating the old. The path to achieving that end is just about as clear, straightforward, and well defined as medical research can ever be. We know what needs to be fixed, and there are numerous proposals for ways to fix it. But the public at large is not yet rallying to this cause.
A cynic might say that they never will, and cite human nature as outlined above. Fortunately, it isn't necessary to persuade everyone. Even a sizable minority will be enough. We can point to successful minority support for research and development in many age-related diseases, for example - large research communities work on the common conditions of aging, despite that fact that everything said about aging and the value of life in the future applies there. There are ways around the basic problem of time preference as it applies to raising support for the medicine of human longevity. We just have to keep working away at it, just like the pioneers who built successful research communities for cancer, heart disease, dementia, and many other conditions that plague the old.