The main reason I won't take my bike out in the winter even if the weather is nice is due to the amount of salt on the roads. Here in the Great Frozen Northeast, there is salt residue on the roads from the first snowfall until at least mid-April. I'll only take the bike out after a few rainstorms have washed the roads clean. The major issue is that when the snow melts, the salt that was dissolved in it becomes a fine white dust on the roads. If you ride on such a road, this salt "dust" gets on everything (engine, wheels) and will start eating through whatever it's on unless you wash the stuff off right away.
Oh, and I had an open bag of Weed & Feed in the garage last winter and I noticed that the exposed zinc bolts on the bike got all whitish. I ditched the Weed & Feed right away.......