It is so sad when it gets to that point. I met Emile Griffith, an ATG HOF boxer, at a HOF show one year where he was deeply into the throes of dementia a bit before he passed away. He signed these cards for me but practically had to be told which end of the pen to use:
It isn't necessarily a case of exploitation, though. There is evidence that it helps people with dementia to engage in activities as best as they are able. It was also clear that Griffith clearly enjoyed the attention and veneration he received from the fans at the show. I am not sure he understood why everyone wanted to meet him and wish him well, but he definitely enjoyed the experience.
The saddest one I ever saw was Jeff Conaway (Bobby Wheeler from
Taxi). He was at a Hollywood memorabilia show at a table signing for fans but sat there sobbing about the pain he was in (a spinal injury and opiate withdrawal). No one went to his table...