Indeed. Someone suggested it is a TV studio rather than a football ground and that seems a fair call. That said, apart from not being able to see the boundary line from parts of Level 3 I think the viewing is, in general, pretty good.
There are a bunch of reasons why you might not go to the games at Etihad. I think the atmosphere is pretty ordinary, the ticketing arrangements are expensive/inconvenient. We don't play very well there and are generally the away team, meaning those without away game entitlements have to fork out cash to see the game.
Since most people don't go to the footy every week it's not surprising they're more likely to go to games at the 'G; If I only attended a few games a year I'd be going to matches at the 'G.