It's just nice having all your games in one location, kind of a pain to have to load up Steam to play one game you bought, load up Impulse to play another game, load up Origin to play your EA games that aren't available on Steam, etc. I also wonder how much it has to do with Steam's terms being "restrictive" (I don't hear other publishers complaining) and if it has more to do with EA just trying to erode Steam's market share by forcing people to use Origin. Although to be fair that's basically what Valve did years ago, Steam might not be nearly as big as it is today if people weren't forced to use it to install and run HL2 and other Valve games.