Well, I feel dumb, I always thought that most of the money came from the publisher.
Anyway, I doubt that even if EA was funding the game that they'd put in-game adverts in it... yet. Battlefield is their mony maker. Hellgate is not. They know that people will buy Battlefield games and that if they put the ads there then they have their audience. Hellgate (I'm looking forward to this game so don't flame me.) is probably not worth the investment. It's a new franchise whos fate is up in the air.
Just my two cents.