Yes because some (most of the ones worth paying for) of the games require some sort of server. So every new player in a game is not free for EA. Giving away a game means they will lose money on this person if they play online.
The costs are also very difficult to determine, where $1 sounds a bit high to me. Lets try to do some random estimates for a random game: 30% of the users wont touch the game whatsoever, and will just have it on their "list". Of the buyers, 0.5% will require some sort of support effort in relation , where 65% are handled by the auto-response and 30% by the first email by an employe.
Say a total of 5,000 downloads are from this "free" coupon for any specific game title. Would $500 or $5000 sound closers to the actually hosting/support cost that the publisher has.
Consider however you have to download Origin to get the games and play them. A feat they've been struggling to get gamers to do, so every gamer that got free games is actually worth a lot to them and probably wouldn't have bought any of these games anyway as they're mostly old and lame.
It's pretty much a win for EA which is why I expect they let it continue so long.
