(Less significant here means a ten year swing in life expectancy. Exercise, not smoking, calorie restriction - these are things that can make 5-10 year expected differences. Everything else is pretty marginal if you exclude the obvious exogenous line items like risk of accident. But an improving implementation of SENS provides indefinite extension of healthy life out to the expected limits due to accident rates, which is somewhere in the 1000-5000 year range for present data).
The mainstream medical research community is largely focused on patching late stage manifestations of aging. Most work and funding goes towards either manipulating proximate causes rather than root causes, or trying to find ways to alter the operation of metabolism to make the disease process less terrible - but again without addressing causes. Until such time as the research community is overtaken by the "address root causes" disruption currently taking place, of which SENS is an exemplar, but by no means the only movement, then progress towards extended life and defeat of age-related disease will continue to be painfully expensive, slow, and marginal.
The trends in life extension achieved through medicine to date are all largely incidental, unintentional. Where aging itself as a collection of processes [1] has been slowed it wasn't because that was the deliberate intent. Again, because until very recently no-one has been trying to address aging itself rather than focusing on the nature of its outcomes. It is the same difference as that between working to reverse or prevent rust in metal structures versus working on repairing structural failures that occur due to that rust.