I believe that is the OP's point.
Fans of certain clubs and the media just loved trumpeting good attendance figures a couple years back as proof of how HUGE their respective clubs were.... but clearly the crowd figures show that all clubs' attendances are linked to on field performance.
When the roosters were consistently good back in the early 2000s our crowds were only rivaled by the dogs in NSW - another early 2000s powerhouse. When we sucked, the dropped back down. Same story for every club, yet for some reason people like to lay the boot into Easts' attendances all the time.
Dragons fans in particular seem to love nothing more than to take credit for everybody else's crwods (see Jason Maher's post in this thread)... despite rarely averaging more than 15-16k, even in the years when they were the clear benchmark side of the competition
But it's the same for everyone, so why the need to lay the boot into the Eels? Aside from a few people, not many Eels fans claim that we average huge crowds. We do claim we have a large supporter base (which is supported by merchandise sales figures, TV figures, memberships, general public sporting Eels merchandising, etc), but we won't claim it's the largest supporter base, as that would be incorrect. Like it or not, Parramatta is an important club for the NRL. Big issue is that we absolutely blow right now, and fans find it tough to go watch them play.
The moment the Storm or Manly or Souths or Roosters or Dogs or whoever starts sucking as much as Parramatta sucks now, and do for two or three consecutive years, their crowds will plummet, too.
We're all passionate about our clubs, but when we are struggling, it is much easier to make excuses to rationalise watching the game at the club or at home, rather than going.
I love the Eels, but even I am not keen on going to watch them live at the moment. It's hard to watch them dish out absolute absolute crap as they have been for three years now.