Compared to the business they used to with the Sims, free to play makes it much, much harder to break even. You're hoping to monetize more off of a smaller percentage of your players. 95% of people will never pay in a free to play game, and the Sims games would sell over 10 million units each, handily, plus expansions. But I know that plenty of people would pirate the expansions, so EA probably sees that as a threat that they need to lock behind an internet connection in a server-based game, and they'll likely destroy the series' profitability in the process.
Compared to the business they used to with the Sims, free to play makes it much, much harder to break even. You're hoping to monetize more off of a smaller percentage of your players. 95% of people will never pay in a free to play game, and the Sims games would sell over 10 million units each, handily, plus expansions. But I know that plenty of people would pirate the expansions, so EA probably sees that as a threat that they need to lock behind an internet connection in a server-based game, and they'll likely destroy the series' profitability in the process.