As I said in the other thread. They didn't want their whole set televised. They wanted the people at Glastonbury to see something the people at home didn't.
The Who were good at Glastonbury a couple of years ago. These older bands did not have benefit of electronics to enhance their performance, especially in the early years, so are more adept at 'live' shows.
They were great for near 70 year olds though!