Maybe your not downloading the entire page, but you are still doing db lookups. If someone has is waiting for moves in 50 games, then all those lookups are being done repeatedly.
Why should these lookups be done, if I'm lookng at one board for 10-15 minutes, figuring a move.
Also, how many people leave a 'my games' page open on a home machine when they go to work , or when they go to bed . All those needless lookups..