That insures you against the long tail of living too long, yes. But if you knew you had exactly 5 years with 99% probability, you wouldn't do that, right?

Also plenty of things are not purely financial. How will you know if this is the last opportunity to see an old friend? As a 34 year old there are plenty of friends I put off catching up with because it will happen someday. As a 71 year old?