Well I haven't read the books, but I did recently have a client who had had a major and catastrophic stroke at the age of 46, and the doctors told his partner that he was in a "locked in state", ie he could not communicate but they thought he could understand. Sadly he died after some months in hospital. He had not granted power of atorney to his partner, no doubt because he felt too young to do that - I was so shocked by the struggle the poor partner had (and they had a small child) with the various authorities, banks, etc, that I got my husband to sign a PoA immediately and also did one myself. I then e-mailed all of the people in my firm and offered to prepare one for them for nothing, and not one person took me up on it - my closest colleague, who is slightly older than me, said she was "not yet ready for that kind of thing" (even though she has several family members, including a husband, whom she could have appointed). The P of A can be made conditional on the attorney obtaining one (or indeed more than one) doctor's letter confirming that you are incapable.
I don't know if the same system operates in the USA and Australia, but as a lawyer I can only urge everyone to take this precaution, - you may well never need to use it, but it could save you and everyone else a great deal of trouble and money.
Rant over! Sorry - it's one of my hobby horses.
Rosemary