Well, Red Faction's Geomod 2.0 took like 6 months to develop, and that's a long time in game development. The buildings are completely physics-based--the dev team had to study up on real-life architecture because their first attempts at buildings collapsed because they were not structurally sound. And the buildings that did exist on the final map were relatively simple buildings, too. I remember maybe 3 stories max for most buildings. If DICE were to have that level of destruction, they'd have to build pretty tall buildings that won't collapse under their own weight. With all of the chaos that happens in a regular match, entire maps would be almost definitely be reduced to rubble by the end of the match, and that would get boring fast. There's very practical reasons for not having such an ultra-realistic destruction engine. Buildings can be built in ways that work best for a multiplayer game, without worrying about making physically stable maps.