I am not going to pretend to know EA's exact reasoning in this particular case but just look at EA's track record for acquiring developers who focus on single player titles then shut them down when they were not able to squeeze every penny from them. I understand that every other major video game publisher does this and this is where the industry is headed, it just sucks.
EA bought and eventually shut down my favorite studio, Maxis. Maxis was the reason I got into PC games, after playing SimCity at my friends house I was hooked. After Simcity 3000 EA bought Maxis and under EA, Maxis released Simcity 4 which was really good. Then about 10 years later a new SimCity gets released at it was an absolute disaster. EA insisted that Simcity be an "always online" game even though it did not need to be and the game was literally unplayable weeks after launch. So after EA botched this launch they shutdown Maxis.
SimCity could not have loot boxes, it would not make sense. Instead of being able to artificially create value in game on existing content and cash in on it, Simcity would have required people to actually create new content. This is what its really about. Look at what the "new" SimCity does, Cities: Skylines, they offer frequent DLC and charge about $10-$12 for new content. Granted this method is basically nickel and diming people but at least there is new content available pretty frequently.