It's not crazy, no one thinks that. My question is why do so many people think of and fear this as a plausible scenario, to the point they prefer to rot and die than see progress in that front. Now this is crazy.
Fortunately for everyone involved, this kind of immortality is not invulnerability, and it doesn't quite save the neurons which are slowly dividing cells, only indirectly limiting damage to them.
So you might have doddering 120 year old ancients (potential predicted life extension) with ever more brain damage.
Because if you were a billionaire who had the ability to make people live forever, why would you let the working class have it and not just keep it for you and your immediate family?
If I were a billionaire and wanted to keep it for me and my immediate family... good luck to me.
How would I be able to enforce it? By somehow keeping the costs high? By lobbying?
Nothing would work, because this would be too big for the working class to just sit there and watch, and if lots of people get really pissed, it can turn very ugly, as history has taught.
People will want it and they'll get it, one way or the other.
So you might have doddering 120 year old ancients (potential predicted life extension) with ever more brain damage.