I think it's too early to draw any sort of conclusion about what this means or why they're doing it. If it becomes a trend with EA-published games, then we can analyze which game types don't have it as opposed to which do, and all the other goodies of that nature.
Until then, it's just one title that doesn't have DRM.
My personal opinion on why? Money.
Even though EA has games that sell very well, EA is not known for their ROI. They are huge, and even though you hear things like CoD selling 10 million copies, Sims 2 selling 10 million, they are still losing money and still laying people off. At the same time, copy protections cost money to use and you don't have to be a genius to realize that Sims 3 is going to sell by truckloads. It would follow that the amount of money they can save by using cheap, light protection would far outweigh any guessable loss to piracy.