I hate to be the advocate of EA here but I'm convinced it's because FIFA is not allowing them to use the trademark any longer and the mentioned loopholes are either permitted by FIFA or will be closed soon.
Nothing to do with previous titles. You could still purchase them. This is EA locking you into playing the current version of the game. Some people like the mechanics of the older games and don't want to have to pay these games that are more store front than actual game.