My AWD sedan is only worse than an SUV for snow driving in a single dimension: ground clearance. I can't drive over snow berms quite as high as those an SUV can. In practice this doesn't matter much, and the sedan is more (vertically) stable in the snow than an SUV. (Yes, I've driven both in these conditions, and vastly prefer the sedan.)
The main issue is that AWD/4WD in sedans isn't that common, while they're nearly standard on an SUV. But that's a matter of market dynamics (people think that SUVs are required for this sort of driving, which is laughable), not any inherent technological or cost limitation.
The main issue is that AWD/4WD in sedans isn't that common, while they're nearly standard on an SUV. But that's a matter of market dynamics (people think that SUVs are required for this sort of driving, which is laughable), not any inherent technological or cost limitation.