In places that get a lot of snow we have good snow removal. Thus you don't need snow tires as you aren't driving in it much. You also learn to drive in snow, which mostly means slow down.
And conversely we read about what anyone in the Midwest would consider to be a minor snowstorm and it causes a catastrophe in the South. See for example this article about 3 inches of snow in Atlanta, Georgia.
That makes sense. Then there is still the problem of the cold tarmac, on which summer tyres are said to have poor grip, but that may not be as obvious to the average commuter as a road turned to thick white with two icy ruts to follow. And anyway I'm getting off topic regarding salt :)
