The premise is that the goal is sufficiently hard and the reward is the incremental advancements. If at the end, the goal is achieved, it's simply cherry on top. If the goal is not achieved due to unforeseen circumstances, it doesn't mean that the life was purposeless as you can very well see the progress made by tracking incremental achievements.
As I said before, its all down to wiring.
Also given the advancements in medicine and increase in life expectancies, I think the chances are a lot many people will live to 60+ so planning life for the worst case may not be optimal.
Another way of putting it is if you talk to lottery winners you’re getting a very biased viewpoint.