Took care of someone with Alzheimers for six years until they passed away. No one should have to exist like that, for that long. A biological shell simply of automatic inputs and outputs. Robin Williams had to hang himself. There should be easy medical options in the US.
I think Alzheimer's is a particularly difficult case. Before diagnosis, many of us imagine that we wouldn't want to exist in a highly deteriorated state with no ability to care for ourselves. But as you start to decline, you still feel like yourself, just a very forgetful version of yourself. On which day do you decide that what remains of your mind isn't enough to make your available future days better than no future days?
The instinct for self preservation is strong. Knowing what will come requires foresight and clarity. You may lose the capacity for informed decision making before the point where it's clear that there's not much to live for.
Many of us lack the insight that Kahneman perhaps had that in order to take control of the end you may need to leave some good days on the table.