They put salt on the roads here, at least in the south. In the north it's too cold even for salt to have an effect so they don't bother. Back inbthe day the cars made inbthe 70's, 80's and 90's used to rust like crazy anless you could find one that had been driven up north. Nowadays they are pretty good at designing the cars to keep the rust away, unless you go for the imported crap. My 18 year old Volvo with 155000 miles on it still doesn't have a single speck of rust on it, neither on top nor underneath.