Why? FWD has better traction because more weight is over the drive wheels, and it's more stable (when rear drive wheels slip the car fishtails)
Well, for one thing, I enjoy drifting/fishtailing when it's raining or there's snow (I only do that if there aren't other cars around though). Having weight over the drive wheels is pretty good for grip yes, but having the drive wheels also doing the steering is not a good thing, especially in unexpected situations. I suppose that a driver that's aware of the limitations of their vehicle will always fare better in poor weather than someone who knows nothing about drive systems and weight distribution, so it just comes down to preference. I prefer RWD (even over all wheel drive).
With thinner tyres, your car is more likely to sink through the snow and get better grip. It's perhaps bad in really deep snow, I wouldn't know.. but for the less than a foot of snow that we usually have on UK roads, it's definitely better with thinner tyres. I've never used real snow tyres, so I don't know about them.