And even when salt is used, cars need a lot more salt per person than other modes of transport does.
Can I get a source on this? I’m not even sure what you mean by it, because salt clears active roadways as much as it does backroads, so how is this being measured “per person”?
Where I live it’s common to spread gravel on the snow to increase grip. And then, of course, it is expected that everyone has the appropriate shoes and bike tires to not slip.
You’re talking about pedestrians, but what about non-pedestrian traffic? The roads are more than just avenues to get to the grocery store, they’re also how the grocery store gets stocked with goods for rising out storms. It how the ambulance gets to you.
And what about the disabled or elderly? Can you get a wheelchair across the gravel?