I dunno. I mean this looks like Steam being greedy, but then I got to wondering...how does Steam function if it can't tell what you own?
For instance, some games come with a lot of DLC material (skins, weapons, etc) already included in the release game. So you paying to unlock them or earning them is something that the authenticating server from the publisher can tell.
But if you have DLC that is closer to an expansion, Steam doesn't know to automatically update your game with that content if you don't have a key associated with it registered to their service. So it would require another level of complexity JUST for EA games, or sending content to people who may or may not own said content.
I can see why Steam doesn't allow it if they are going to open themselves up to a lot of headaches and issues with no monetary incentive just to please one publisher.
It sucks for us, but other distribution systems that I've experienced such as D2d and the like are not like Steam...you just get a starting point for the game then you have to seek out all the patches and what not afterwards.