As an older guy I can assure you personally that when I have free time, the last thing I want to do with it is watch TV. Too much living to do.
I do agree with your observation about old people and TV in that my experience with elderly ancestors is an extremely high correlation between watching TV all day and death within the next couple years. When you can't do anything anymore physically but open your eyes, the socially accepted dumping ground (at least on a small scale) is in front of a TV. I believe this explains the peculiar claim that 80 year old people "watch" 16 hours per day of TV on average. This does not explain the claims about 50 year olds.