They don't make money from used game sales, resale stores like Gamestop do.
While this is a very questionable move from a consumer standpoint, it makes business sense.
MMOs rightfully charge for multiplayer access, however they have servers to maintain and use the resources acquired to improve their game and keep it fresh.
One could argue that if EA wants to make this idea appealing to customers, they should offer new content for free for the paying subscribers of used games, or those who paid for a new game.
Then again, they may just charge us for cheat codes and "VIP" mode like they have in the past. Even if one were to buy the game new.