Thats because SLI doesn't work correctly, some have had a little success but at the price of artifacts showing etc... Luthier said it was fixed, he also said in development that it would work, both these were untrue.

Nvidia will not look at CLOD for a long time, it would be impossible for them to get to grips with the game as it is far to bugged. You can imagine Nvidia saying " you want us to make a SLI profile for this, when you have no FSAA, you have stuttering, shimmering and pop up buildings?" The dev's have no idea what they are doing regarding SLI & FSAA so what chance have Nvidia got of sorting it?