Has nothing to do with old age, or lack of memory -- when you have a LOT of things on your plate, maintaining lists helps you manage a large number of things -- particularly maintaining items with a far off due date on your radar and in focus.
I don't particularly care about grocery lists -- but I do maintain them for :
- items to pack for my next trip.
- things to do on my next trip (so I can get them done on the first 1-3 days)
- projects to complete, and their state of completion
etc....
I can see how for most people, lists are not important, as they have next to nothing of real importance to manage.
Lists are one of the differences between successful and efficient people, and those who are not.