At root, medicine is driven by the urge remain alive. It is a process of engineering the means to prevent death, and so setting out to deliberately create greater longevity by tackling the root causes of aging - rather than addressing named diseases, one by one - is no more than the logical next step in this process. We know more than enough to get started down this path, and there are some few organizations working on it even today, though far from enough and with far from enough funding.
Consider a world with the means to prevent aging - say, though a package of therapies that a person undergoes every twenty years or so. Infusions of fresh stem cell populations, engineered enzymes to degrade metabolic waste products that build up in and around cells to impair their function, some form of mitochondrial DNA repair, culling excess memory T cells, and so on. These therapies prevent and reverse the build up of damage, allowing a body to continue in good health indefinitely. There is no good reason for them to be any more expensive than your average run of clinical treatments today: they would require little time from a physician, and would operate in much the same way for everyone, allowing economies of scale in production and distribution.
In such a society, all of the pressures associated with the short span of life we presently enjoy evaporate. We are so steeped in that omnipresent pressure of time that it's somewhat hard to envisage what a society without it would look like. Every strategic decision that we make in the course of our lives is based on time - that we have ever less of it remaining, the clock is ticking, and have only a few shots at getting anything significant accomplished. It requires a decade to become truly talented in any particular profession or skill, for example, and at least a few years to figure out whether not we can follow through to that level. That is a vast investment of time when we only have a few decades in which we are at our prime. The same goes for careers and relationships of any significance. We are pressured and choices have great weight precisely because we must forever give up an ocean of possibilities in order to swim in any particular pool.
There is a related school of thought among those opposed to engineering longevity: they say that the pressures of time created by the fact that we age to death due to our inadequate medical technology are a good thing. To me this has the look of rushing to justify what is, regardless of what might be, but they argue that the industry of individuals and humanity as a whole requires the deadline of dying; that without it, no-one would accomplish anything. They look upon the unending holocaust of death and destruction caused by aging - 100,000 lives every day, all they knew, all they could accomplish in the future, all they might have done, erased - and say it is necessary.
This is a hideous nonsense, serving to illustrate that little but a veneer separates us from the barbarians who actively slaughtered millions in past decades. It is true that rapid progress is very necessary in today's world - but we need it because we are dying, and the only way to save ourselves is through technological progress. The faster the better, every increment of speed representing countless lives that might be saved on some future date. If more people were more aware and more interested in doing something about this, we might move faster yet towards the biotechnologies of rejuvenation. Unfortunately, for all that each and every human life is shaped completely by the foreknowledge of future disability and death, all too few are willing to help change this state of affairs.
But so what if the medical technologies that can prevent death by aging make our societies slower-paced, more considered, less energetic? I'm not of the mind that this is a terrible thing - free-wheeling use of a resource is characteristic of wealth, and when we are wealthy in time, we will have the luxury to use it in ways that presently make little sense, or are called wasteful. Caring about waste is a sign of poverty, a sign that we don't have enough of whatever we worry about wasting, which in turn suggests we should do all we can to accumulate more of it. Besides, I don't for one moment believe that the slowing of economic engines and technological progress will in fact happen as feared by those who advocate for the continuation of mass death and suffering. There are all sorts of economic pressures upon human action that have next to nothing to do with aging and our current all-too-short span of life: consider the shifting desires for security, food, property, knowledge, and novelty, for example. The timescales on which those urges operate will not much change in an ageless society, as people will still have the same human nature as exists today. There will continue to be dynamic and ever-changing industries devoted to keeping people fed, clothed, and entertained.
These responses to irrational fears are, at the bottom line, unnecessary to some degree. 100,000 people died today of a cause that we can do something about. Tens of millions die every year, and hundreds of millions more suffer terribly on their way to that end. There is no argument that can possibly outweigh the need to address what is by far the greatest cause of death, suffering, and loss in the world - yet, for some strange combination of reasons, many people keep trying to find one.